Using Databases to Solve Problems
CHAPTER 9 QUERYING A DATABASE IN MS ACCESS
Thus far we have discussed the structure of relational database and how to plan and create a
database. Once the database is created and data placed in the appropriate table, we will need to
be able to extract data. The data in a database can be retrieved by examining its tables; however,
all the information contained in a table is frequently more information than is needed by a
database user. In addition, database users often want to view information that spans related
tables, or view data in a different order. Queries provide a way for users to obtain more
meaningful information from a database that simply viewing all data contained in a table.
Queries can be used to:





Filter data by selecting specific records according to criteria.
Sort records.
Group records together (aggregate) to perform calculations such as Sum, Average,
Count, Min, Max, etc.
Perform arithmetic and Boolean calculations.
Extract information from more than one table by joining related tables.
This chapter will cover the first four bullets; the last item, joining tables, will be discussed in
subsequent chapters.
WHAT IS A QUERY
Remember that a table is a database object that stores records of related data according to a
prescribed field order. A query is also an Access database object; a query defines how data will
be extracted from existing data tables or the results of previous queries and how the extracted
data will be organized. In English, a query is a question. In a database, a query is a set of
instructions the computer will follow to answer a question about the data in a
database. The answers themselves are dynamic, it changes whenever the data in the database
changes, and thus is not part of the query but rather the result of the querying operation. The
results of a query are often referred to as a dynaset.
Specifying and performing a query involves the use of relational algebra operations such as
select, project, join, etc. Several languages exist that can be used to create database tables,
relationships, and queries. One of the oldest is SQL, which stands for Structured Query
Language (pronounced "SQL" or "see-qwill"). It was originally developed by IBM for use on its
mainframe computers. Fortunately, in modern day databases, we will neither have to
understand how to write instructions in SQL or the process by which the computer actually
obtains the dynaset. A user of Microsoft Access can specify a query using a tool called Query by
Example (QBE). This approach makes use of the graphics capabilities of the computer (GUI
interface) to allow the user to select the elements required for a query. The software then
translates QBE grids into SQL for processing by the computer.
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Using Databases to Solve Problems
Before we can begin to use the query tool, we or someone else must have already completed the
following tasks:



Created tables with defined fields, field properties, and primary keys.
Entered data into the tables.
Set up relationships between the tables using foreign key(s).
The next section will describe a sample database that meets these requirements and will be used
to demonstrate the query throughout the chapter.
A SAMPLE DATABASE
In order to illustrate some of the query operations we will utilize the sample database seen in
Figure 1.
Members
ID#
635
534
345
546
903
002
047
Name
Acquila, Jose
Adler, Lawrence
Amico, Donald
Anderson, William
Applegate, Bernice
Aston, Martin
Attwater, Lester
Phone
614-927-8345
614-746-2385
419-345-8472
513-345-9384
513-485-3833
614-485-3888
614-292-1442
Address
Pickerington, OH
Pataskala, OH
Toledo, OH
Cincinnati, OH
Cleveland, OH
Columbus, OH
Columbus, OH
Active
Yes
Yes
Yes
No
Yes
No
Yes
Join Date
1/5/97
3/4/99
1/5/97
4/10/00
3/17/01
11/7/98
9/1/00
Finances
ID#
635
534
345
546
903
534
Dues-Paid
100
50
100
0
0
50
Donation
0
0
50
250
0
20
Figure 1: Club Database – Database
View of Tables
This database contains two tables: Members and Finances. The table structures are as follows:

Members(ID#,Name,Phone,Address,Active,Join Date) This table is a membership
list of all active and retired members. The ID# is a Number data type and has been
identified as the primary key for this table. The Active field is a “Yes/No” Boolean data type
field (a yes indicates this is an active member). The Join Date field is a date data type field.
All other fields in the Members table are Text.
Note that when typing a Boolean field into an Access table, the column is usually displayed
as check box. In this case, a check indicates that this is an active member; no check indicates
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Using Databases to Solve Problems
a past or retired member. The actual values stored are the Boolean values. If an Access table
with a Boolean field is copied into an Excel spreadsheet, the Boolean values are translated to
True/False cell entries.

Finances(ID#,Dues-Paid,Donation) This table contains records of member
transactions. The amount of dues paid (full or partial payment) is entered in the Dues-Paid
field. Dues for the year are $100 for active members; retired members are not charged dues.
Additional contributions are recorded in the Donations field. The ID# field is type Number
and Dues-Paid and Donation fields are type Number. A member may make any number of
transactions.
Both tables contain and an ID# field representing the same information. Both these fields are
defined as type Number. ID# is the primary key of the Members table. Thus all three
requirements are met to set up a relationship (same information, same data type, primary of at
least one table). The ID# fields create a foreign key relating the two tables, as diagrammed in
Figure 2. We have now completed setting up the database relationships and are ready to ask
questions about the database.
Members
Primary key: ID#
ID#
Finances
Primary Key: none
Figure 2
USING THE QUERY DESIGN TOOL
In Access, the query object contains the instructions the computer will carry out to answer a
specific question about the data in an Access database. These instructions tell the computer
what set of data needs to be examined, and what filters and/or sorts to apply. Executing an
Access query results in a dynaset, a set of data based on the most recent information in the
database.
THE QUERY BY DESIGN TOOL STRUCTURE
There are two different ways to use the query tool in Access; one way is to follow a set of steps in
the Query Wizard and the other is to use the Query Design tool. Both of these options can be
launched from the Create ribbon in the Other group. This chapter will deal exclusively with the
latter option, the Query Design tool. Figure 3 displays the Query Design tool window including
the Show section and the QBE (query by example) grid. Figure 4 displays the content sensitive
Design ribbon containing the different design commands available.
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Transaction Table
added to QBE grid
Figure 4
Account# &
Transaction$
fields selected
Figure 3
In the upper portion of Design window, the data objects needed for the query (either tables or
previously created queries) are displayed. In the lower portion on the QBE grid, the user
specifies the fields, criteria, sorting, and information needed to carry out the query. This section
is divided into a series of rows as follows:

FIELD: Lists of all the fields involved in the query.

TABLE: For each field entered, the table it came from must be listed. Sometimes two tables
may have a field with the same name so the table is necessary to distinguish the fields.

TOTAL: This line is normally not shown. It can be toggled using the  toolbar button. It is
used in queries that require grouping of data.

SORT: This line is used when sorting. One or more fields can be organized in Ascending or
Descending order.

SHOW: This box is checked by default and is used to specify whether or not the field will be
shown in the resulting dynaset.

CRITERIA: This specifies criteria that a field must meet in order for a record to be included
in the resulting dynaset. e.g., Donation >= 200.

OR: This specifies any alternate (Boolean Or) criteria.
The mechanics of selecting the data objects and selecting the appropriate fields is covered in the
course textbook. Here, the focus will be on which design elements are needed to solve specific
problems.
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Using Databases to Solve Problems
FILLING OUT THE QUERY GRID
The design grid in Figure 5 is a query that lists
the Name and Address fields from the Members
table. The Show line indicates that both of
these fields will be displayed in the resulting
dynaset. The other fields on the Members table
are not listed on the grid and therefore will play
no role in either the dynaset display or the
selection of records. The resulting dynaset for
Table: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
this query will display these two fields for all
records in the Members table, as there are no
criteria specified to filter the data.
Address
Members
x
Figure 5
How can a question be translated onto the QBE grid? As with any problem solving activity, it
helps to have a methodology containing a set of logical steps to follow. The following is a
simplified method for taking a question and translating it into a QBE grid. This procedure will
be extended in later chapters to allow for the use of multiple tables in a query.

Step 1: Plan the QBE grid:
When filling out the QBE grid it is always wise to plan ahead, since the next task will be to
select the table to be included in the query. In order to know which table (or previous query)
is required, the following information must be known:

o
What fields are to be shown in the resulting query and in which table (or previously
written query) can these fields be found?
o
What field(s) will be filtered and therefore what criteria should be specified for that
field? For example, if only a list of active members is desired, the criterion Yes must
be specified in the field Active.
Step 2: Add the Table:
Using the Show table feature add the table(s) or saved
query required for the query. The Show Table dialog box
can be launched using the Show Table button on the
Query Setup group of the Design ribbon. The Show Table
dialog box can be seen in Figure 6. Select the desired
table (or query) object in the dialog box by double
clicking on the object name or clicking on the object and
then the Add button.
Figure 6
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Using Databases to Solve Problems

Step 3: Fill out the Grid:
1. List each of the fields to be shown on the resulting dynaset. Select the fields from the
table(s) shown. The detailed mechanics are described in the course text.
2. List any fields not shown but that will contain criteria. Make sure to uncheck the show
box for such fields.
3. Write the necessary criteria in the appropriate fields using the Criteria and OR lines.
4. Use the Sort feature, Group by feature, and Expression builder as needed.

Step 4: Save and name the query.
SELECT QUERIES
This section discusses writing queries that select specific records based on a set of criteria. This
includes a single select criterion in a single field, multiple criteria in a single field, and multiple
criteria in multiple fields.
QUERIES WITH A SINGLE CRITERION
First, the methodology described in the previous section will be used to create a query
containing a single condition on a single field. A condition can be specified by using the Criteria
line of the QBE grid. Consider the following example:
Write a query to select all active members, listing their names and addresses. The
results should be similar to structure/data listed in Figure 7.

Step 1: Plan the QBE grid. The query specifies that the
Name and Address fields are to be shown in the
resulting dynaset. Both are found in the Members
table. In addition, a criterion that only “active
members” should be included on this list is specified,
requiring a condition on the Active field (i.e., that it is
equal to “Yes”), which also is on the Member’s table.
Name
Address
Acquila, Jose
Pickerington, OH
Adler, Lawrence
Pataskala, OH
Amico, Donald
Toledo, OH
Applegate, Bernice
Attwater, Lester
Cleveland, OH
Columbus, OH
Figure 7

Step 2: Add the Member’s table on the QBE design view in Access. All information needed to
answer the question is found in this table

Step 3: Select the appropriate fields (Name, Address, and Active) and place them in the grid.
Since Name and Address are to be shown in the dynaset, be sure the Show checkbox for each
is checked. Uncheck the show box for Active, as this field requires a criteria but is not asked
to be shown in the final result.
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Fill in the selection criteria on the Criteria line of the QBE grid. Place the criteria, in this
case, in the Active field column on the Criteria line. Since this is a Boolean type field the
criterion can be either Yes or No. Since only Active members are specified, the criterion will
be Yes. Quotes should not be used around Yes since it is a value in a Boolean field and not a
text label.

Step 4: Save the QBE grid by naming the query Query1. The final version of the QBE grid can
be seen below (Figure 8).
Tables: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
Address
Members
Active
Members
x
Yes
Figure 8 – Query 1
Logically, what steps are required to obtain this dynaset? To obtain this result, one would
systematically go through each record of the Members table and test to see if the criteria are
met. If the criteria are met (in this example, the member is active), then the appropriate fields
for that record should be displayed. Notice that the records for Aston and Anderson do not
appear since they are not active members.
Another example of how a QBE grid is designed to answer a question with a single criterion is as
follows:
Write a query to list the names and addresses of all Members who live in Bexley,
Ohio.
Table: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
OR
Address
Members
x
“Bexley, OH”
Using the methodology outlined, the QBE grid can
be written as seen in Figure 9. Notice the criterion,
“Bexley, OH”, is a criterion on a text field and
therefore requires quotation marks.
If you run this query you will discover that the
dynaset contains no records, since none of the
members live in Bexley.
Figure 9 – Query 2A
Is it a good idea to have a field in a database that contains both the city and state combined, as is
the case in the example database? This is probably not the best way to organize data in a table
as the city and state is not an inseparable unit. At times only the city or only that state may be
needed. A better way to have designed the original table would have been to make these two
pieces of information separate fields.
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Using Databases to Solve Problems
Write a query to list all club members and their addresses.
Such a query contains no criteria. The two fields containing the required information should be
placed on the QBE grid and the criteria row should be left blank, as seen in Query 2B.
Table: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Address
Members
x
Figure 10 – Query 2B
USING RELATIONAL OPERATORS IN QUERY CRITERIA
It is also possible to use relational operators to specify criteria on a QBE grid. For example:
Write a query to list by ID# all transactions with donations of greater than $0.
Show the ID# and donation amount.

What fields will be shown? ID# from the Finances table and Donation amount from the
Finances table.

What fields will have criteria that are not shown? No additional fields

What criteria are needed? The donation field will have the criteria >0. This should be
inserted on the grid in the column containing the Donation field on the row labeled Criteria.

What table(s) are needed? All fields used are from the Finances table.
The query grid and resulting dyanset are shown in Figure 11.
Table: Finances
Field
ID#
Table
Finances
Sort
Show
x
Criteria
OR
Donation
Finances
x
>0
Criterion in
Donation field
id#
donation
345
50
546
250
534
20
Figure 11 - Query 3A
To specify a greater than criteria, use the greater than operator followed by the value. The syntax
does not include quotes when using a numerical type field. The following relational operators
can be used in an Access query.
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Equal to: =
Greater than: >
Greater than or equal to:
Query 3B
Field
Table
Sort
Show
Criteria
OR
Table: Members
Name
Address
Members
Members
x
< “m”
Figure 12
x
>=
Not equal to: <>
Less than: <
Less than or equal to:
<=
Relational operators also work equally as well on text
fields. A criteria of < “m” will result in all records where
the value in that field begins with the letters A through L.
This is illustrated on the Query 3B QBE grid in Figure 12.
MS Access query criteria are not case sensitive; therefore
M and m are treated identically. This is not the case for
other DBMS software packages. Also notice the criteria,
but not the relational operator, is enclosed in quotes.
Criteria for text fields, unlike numerical fields, require
quotation marks around the text.
WILD CARDS IN CRITERIA FOR TEXT FIELDS
Another tool that can be used when writing a criterion on a text field is to use a wildcard. The
* wildcard can be used to replace one or more characters. The ? wildcard can be used to replace
a single character. Whenever a wildcard is included in a criterion the expression Like must
precede the expression.

Like “J*” - this tells the computer the criterion is anything that starts with a J no matter
how many characters it has or what they are: Jay, Justice, Jo, would all meet the criteria

Like “t*p” – this tells the computer the criterion is anything that starts with t and ends with
p. top, tip, tekdp all would meet the criteria.

Like “*4*” – this tells the computer the criterion is any entry that contains the character 4.

Like “?d” - this tells the computer the criterion is anything that ends in d and has one
character in front of it. Id, bd, od would all meet the criteria. Tad would not meet this
criteria

Like “s??n” – this tells the computer the criterion is anything that is four characters that
begins with s and ends with n. sean, soon, sxxn would all meet this criteria.
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Write a query to list all members who have phone numbers that begin with 614.
The QBE grid (Query 4 – in Figure 13) and resulting dynaset are as follows. Notice that since
614 is part of a text field, the numeral characters are enclosed in quotes.
Tables: members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Phone
Members
name
Acquila, Jose
Adler, Lawrence
Aston, Martin
Attwater, Lester
Like “614*”
Figure 13 – Query 4
QUERIES USING MULTIPLE CRITERIA IN A SINGLE FIELD:
The examples shown thus far have been limited to using a single criterion – one condition in one
field. Often multiple criteria are required to obtain the desired record set. An example of
multiple criteria in one specific field is as follows:
List the names of all members who either live in Pickerington or in Columbus.
The QBE grid to list the members’ names either living in Pickerington, OH or in Columbus,
OH is seen in Figure 14.
name
Acquila, Jose
Aston, Martin
Attwater,
Lester
Table: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
Address
Members
“Pickerington,OH” OR
“Columbus, OH”
OR
Figure 14 – Query 5A
Notice the use of the Boolean operator OR within the Criteria Box of the QBE grid. The OR
operator in Access has the same meaning as the one in Excel, but the syntax is different.
Another way the same criteria can be written is to place the OR item on a separate line. These
OR lines assume that any item listed has an “or” relationship to the criteria above. An example
of this alternate QBE design is seen in Query 5B on Figure 15. The resulting dynaset will be
identical to the one generated in Query 5A.
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Table: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Address
Members
“Pickerington, OH”
“Columbus, OH”
Figure 15 – Query 5B
Another example: List the ID#s and transaction amounts for all donations
between $50 and $100.
The criteria here can be interpreted as >=$50 and <=$100. The QBE grid would be as follows:
Table: Finances
Field
ID#
Table
Finances
Sort
Show
x
Criteria
OR
Donation
Finances
id#
x
345
donation
50
>=50 AND <=100
Figure 16 – Query 6
Notice that the Criteria box for the Donation field in Figure 16 contains a familiar Boolean
operator, AND, again with a different syntax than seen in previous applications. The resulting
dynaset contains only one record. Only member 345 made a donation between 50 and 100
dollars.
Another valid syntax to express >=$50 and <=$100 is between 50 and 100.
Can the AND operator be eliminated and the second criterion (<=100) placed on the next line of
the grid? No, the OR lines represent “or” operations only.
What if the criteria in the donation field looks like this: $50 AND $100? Logically, no single
record can have both a $50 value and a $100 value in the donation field simultaneously. Thus
no records will be selected.
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QUERIES USING A MULTIPLE CRITERIA IN A MULTIPLE FIELDS:
The next step in learning how to set up QBE grids is representing multiple criteria in multiple
fields. Consider the following example:
List the names of all Active members in the Columbus area.
Here there are criteria is on both the Address and Active fields simultaneously. Both of these
criteria must be met for a record to be selected. This indicates an AND operation is needed. To
represent an AND relationship between two or more fields on a QBE grid, place the criteria
on a single line. So the resulting grid and dynaset for this example would be (Figure 17):
Tables: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Address
Members
Active
Members
name
Attwater, Lester
“Columbus, OH”
Yes
Figure 17 – Query 7
Now consider the case of listing all active members from Columbus and all inactive
members from Cincinnati. Include the members name, address and active status. Here we
have the following logical operations:
EITHER
Address is Columbus AND Active is Yes
OR
Address is Pickerington AND Active is No.
To express the AND operation place the criteria on the same line. To express the OR operation,
place one set of criteria on one line and the second set on the other. Thus the resulting QBE grid
and dynaset will look like the following:
Tables: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Address
Members
Active
Members
x
“Columbus, OH”
“Cincinnati, OH”
x
Yes
No
name
Anderson, William
Attwater, Lester
address
Cincinnati, OH
Columbus, OH
active
No
Yes
Figure 18 Query 8
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Using Databases to Solve Problems
QUERIES WITH SORTING:
The use of the Sort feature to temporarily organize records on tables was discussed in Chapter
2.1. A similar but more powerful feature is available in the query tool. To sort a field in a query,
select the field to be sorted and indicate the sort order (Ascending or Descending) on the Sort
line of the QBE grid. Sorting can be combined with any other set of criteria.
SORTING ON A SINGLE FIELD
Consider the following problem:
Write a query that will list the names of all Members, their address and join date.
List them in order of join dates, with the most recent first.
Tables: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Address
Members
x
Join Date
Members
Descending
x
Figure 19 – Query 9
Name
Address
Join
Date
Applegate, Bernice
Cleveland, OH
3/17/01
Attwater, Lester
Columbus, OH
9/1/00
Anderson, William
Cincinnati, OH
4/10/00
Adler, Lawrence
Pataskala, OH
3/4/99
Aston, Martin
Columbus, OH
11/7/98
Acquila, Jose
Pickerington, OH
1/5/97
Amico, Donald
Toledo, OH
1/5/97
To accomplish this sort, the word Descending is added to the grid on the Sort row in the
corresponding field column. Dates, much like in Excel, are represented by values, where the
lower the value the earlier the date. Thus to sort the Join Date field by most recent date first, the
word descending is used. The word Ascending is used to sort from smallest to largest value
(earliest date first). When entering a sort, click on the Sort row in the column desired, and
choose either Ascending or Descending from the drop-down list.
SORTING ON MULTIPLE FIELDS
Again consider the same query but this time sort by address and then by join date. This
requires sorting on multiple fields. The question is which field is sorted first – which field is the
major sort and which field is the minor sort? Should the list have (1) all like addresses together
organized by join date, or (2) all like join dates together organized by address (Figure 20)?
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(1)Sorted First by City then Date
(2) Sorted first by Date then City
Cincinnati, OH
4/10/00
Pickerington, OH
1/5/97
Cleveland, OH
3/17/01
Toledo, OH
1/5/97
Columbus, OH
11/7/98
Columbus, OH
11/7/98
Columbus, OH
9/1/00
Pataskala, OH
3/4/99
Pataskala, OH
3/4/99
Cincinnati, OH
4/10/00
Pickerington, OH
1/5/97
Columbus, OH
9/1/00
Toledo, OH
1/5/97
Cleveland, OH
3/17/01
Figure 20
Notice that the order of the records in each dynaset differs. In case (1) the location field is the
major sort and the date field is the minor sort. In case (2) the date field is the major sort and the
location field is the minor sort. How is the sort order specified on the QBE grid?
Thus far the order of the selected fields on a QBE grid has not been important as it has only
impacted the order of the fields displayed and not which records are selected. However, when
trying to sort records into a specific order with multiple sort fields, the order of the fields listed on
the QBE grid is critical to obtaining the desired outcome. The placement of these fields on the grid
will determine which field is the major sort and which fields are the minor sorts. In other words,
the order of the fields in the QBE grid determines the order of the records in the resulting dynaset.
When executing a query, first the computer selects the requested records based on the given
criteria. Then the computer sorts the records. It looks through the Sort row form left to right,
sorting the first field it finds in the QBE grid with sorting instructions. Then it continues to the
next column, sorting as instructed but this performing the minor sorts within the major sort
groupings. The next column is then considered for a minor sort, and so on. Sorted fields need not
be the first field nor adjacent to each other, but their order must be major sort first, then minor
sort 1, minor sort 2, etc. The QBE grid for (1) is Figure 21 and for (2) is Figure 22:
Write a query that will list the names of all Members, their address, and join dates.
Sort the list by address and then by join date (most recent first).
Tables: Members
Field
Table
Sort
Show
Criteria
OR
OR
Name
Members
x
Figure 21 – Query 10 Sort (1)
Address
Members
Ascending
x
Join Date
Members
Descending
x
Name
Address
Join Date
Anderson, William Cincinnati, OH
4/10/00
Applegate, Bernice Cleveland, OH
3/17/01
Attwater, Lester
Columbus, OH
9/1/00
Aston, Martin
Columbus, OH
11/7/98
Adler, Lawrence
Pataskala, OH
3/4/99
Acquila, Jose
Pickerington, OH
1/5/97
Amico, Donald
Toledo, OH
1/5/97
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Write a query that will list the names of all Members, their address, and join date.
Sort the list by join date (most recent first) and then by address.
Tables: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
OR
Join Date
Members
Descending
x
Address
Members
Ascending
x
Name
Join Date
Address
Applegate, Bernice
3/17/2001
Cleveland, OH
Attwater, Lester
9/1/2000
Columbus, OH
Anderson, William
4/10/2000
Cincinnati, OH
Adler, Lawrence
3/4/1999
Pataskala, OH
Aston, Martin
11/7/1998
Columbus, OH
Amico, Donald
1/5/1997
Toledo, OH
Acquila, Jose
1/5/1997
Pickerington, OH
Figure 22 – Query 11 Sort (2)
Re-write Query 11 to only display records for members who joined before January 1,
2000.
Use the exact same QBE grid, but include a criterion in the Join Date field. Note that when typing
in dates, # signs are used before and after the date. Dates can be expressed as mo/day/yr #1/1/2000#, or they can written out as follows - #January 1, 2000#. The # allows Access to
determine that #1/1/2000# is January 1, 2000 and not the number 1 divided by 1 divided by
2000. Figure 23 is the QBE grid and resulting dynaset for this query.
Tables: Members
Field
Name
Table
Members
Sort
Show
x
Criteria
OR
Join Date
Members
Descending
x
Address
Members
Ascending
x
<#1/1/2000#
Name
Join Date
Address
Amico, Donald
1/5/97
Toledo, OH
Acquila, Jose
1/5/97
Pickerington, OH
Aston, Martin
11/7/98
Columbus, OH
Adler, Lawrence
3/4/99
Pataskala, OH
Figure 23 – Query 12
AGGREGATING FIELDS USING QUERIES:
How much has each member donated in total? To answer this question manually requires going
through each transaction record and adding up the donations for each specific member number.
For example member 534 has two transactions listed: one with a donation amount of $50 and the
other with a donation amount of $0. Thus the total donation amount for member 534 is $50. This
process will need to be repeated for each member id to find the total for each member.
Access queries can be used to accomplish this same task using a feature known as Aggregate
Functions. This feature can perform tasks such as counting all the members living in Columbus,
Page 15
Using Databases to Solve Problems
OH, totaling the dues or donations by ID#, or even to determine the average donation amount.
Microsoft Access has the following built in aggregate functions: Sum, Avg, Count, Min, Max,
Stdev, Var, First, Last. This aggregation of data may be done on all selected records or in
specific groupings using the Group by specification in the desired field.
Look at the QBE grid below that counts all members by location. The resulting dynaset
should have a record for each location and a “count of …” field containing the number of records
for that location.
Tables: Members
Field
Address
Table
Members
Total
Group by
Sort
Show
x
Criteria
OR
ID#
Members
Count
x
address
Cincinnati, OH
Cleveland, OH
Columbus, OH
Pataskala, OH
Pickerington, OH
Toledo, OH
CountOfid#
1
1
2
1
1
1
Figure 24 – Query 13
Aggregating is specified on the Total line of the QBE grid. This line does not automatically
appear on the grid. To display the Total line, click on the  button in the Design ribbon. If an
aggregate function is specified for any field in the grid, the total line must be filled in for every
other field in the grid. The Total boxes in the row must be filled in either with a Group by, a
function (Count,Sum, Avg etc), Where (in fields with criteria), or Expression(for calculated
data).
The grid in Figure 24 groups the Address field so that all like entries in this field (Columbus
entries, Toledo entries, etc) are put together into a group. Then within each group, the
records in that group are counted using the ID# field. Notice that in the resulting dynaset, the
field name for this counted field is now referred to as CountofID# instead of ID#.
In the example above, the records in the ID# field of the Members table were counted. This query
would work just as well if the phone number field or any other field were used to count the records
in this grouping. The new field names in the dynaset would then correspond to the field used,
CountofPhone etc. However, when summing a field (or using min, max, average or stdev) only the
field being summed may be used, as demonstrated in a later example.
Also consider what happens if the Names field were to be included in a query to count the number
of members by location? Consider that each grouping of city may include many different members
and thus many different member names. If the query is grouped by Name and City, the computer
will automatically group by the smallest level of detail, in this case Name. Hence, the subtotal
calculated will no longer be for each city as desired, but for each Name. Thus, it is necessary to
plan the groupings to correctly reflect the level of aggregation.
Page 16
Using Databases to Solve Problems
How many active members reside in each city?
Modify the QBE grid from query 13 to include the field Active with the criteria YES. Then in the
Total row include a Where to tell Access that only records meeting this criteria should be
included in the count. Fields with a Where (criteria) should not be shown. Will the results be
different than that of Query 13?
Tables: Members
Field
Address
Table
Members
Total
Group by
Sort
Show
x
Criteria
OR
ID#
Members
Count
Active
Members
Where
x
Yes
address
Cleveland, OH
Columbus, OH
Pataskala, OH
Pickerington, OH
Toledo, OH
CountOfid#
1
1
1
1
1
Figure 25 – Query 14
By ID#, create a summary listing the total dues-paid and the average donation made.
Assume each member can have multiple dues and donation payment transactions. The QBE grid
and resulting dynaset are illustrated in Figure 26.
Tables: Finances
Field
ID#
Table
Finances
Total
Group by
Sort
Show
x
Criteria
Dues-Paid
Finances
SUM
Donation
Finances
AVG
x
x
id#
SumOfdues-paid AvgOfdonation
345
100
50
534
100
10
546
0
250
635
100
0
903
0
0
Figure 26 – Query 15
Recall member 534 had two transactions. One transaction was a $50 dues payment; the other was
a $50 dues payment and a $20 donation. Notice that the aggregated values displayed for member
534 are $100 in total dues payments and $10 in average donations per transaction. As previously
mentioned, unlike the Count function the other aggregate functions such as Sum, Avg, Min, Max
must be used only on the field being summed, averaged etc.
How can the total dues paid by all members and the overall average donation made
by members be obtained? It would look almost the same as Query 15, but exclude the ID#
field grouping (Group by). Query 16 details the results; notice only a single record containing
these values is returned.
Tables: Finances
Field
Dues-Paid
Donation
SumOfdues-paid AvgOfdonation
300
53.33
Table
Finances
Finances
Total
Sum
Average
Figure 27 – Query 16
Sort
Show
x
x
Criteria
Page 17
Using Databases to Solve Problems
USING CALCULATED FIELDS IN QUERIES:
One of the cardinal rules when writing databases
is never to repeat information or store
information that can be easily generated from
existing data. Consequently, when information
such as the total value of a transaction (dues plus
donation) is needed, a query can be written to
obtain it instead of storing it permanently in a
table. The Access Expression Builder tool
found on the Design ribbon in the
Query Setup Group can be used to write
expressions in queries. As with any software tool,
there is a specific syntax which must be used, and
a library of available functions.
Figure 28 – Expression Builder
The Expression Builder dialog box, as seen in
Figure 28, allows the user to select the object desired (table, saved query, function) from the
hierarchical list in the left bottom section of the Builder. Once the object is selected, the fields
available from that object will be listed in the center bottom section. By double clicking on these
fields they can be added to the expression being built in the top box of the Builder.
USING THE EXPRESSION BUILDER TOOL – A SIMPLE EXAMPLE:
Consider the follow problem: Write a query that adds Dues-Paid to the Donations for
each transaction.
To create a query to calculate these values from the existing data fields, follow the steps below:








Start a new query and show the appropriate table – Transactions.
List the ID# field on the QBE grid.
From a blank QBE grid box (fields row) select the expression building button to launch the
Expression Builder tool.
To select the first operand, Dues-Paid, first select the Transactions table object from the
hierarchical list of available objects (tables, queries, etc.) in the left bottom box.
Once the object is selected, the available fields for that object will appear in the center box of
the Expression Builder. Click on the field required, in this case Dues-Paid.
Click on the + operator just below the Expression section or simply type a plus sign in the
Expression box next to Dues-Paid.
Add the second operand, Donations, using this same methodology.
Click the OK button when the expression is completed.
The resulting expression should look something like this:
Exp1:[Finances]![Dues-Paid] + [Finances]![Donations]
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Using Databases to Solve Problems
Notice the expression syntax which is generated: each object (table, field) appears inside of
brackets [ ], and that table names are followed by an exclamation point (!). Use this syntax when
writing expressions.
Also notice that this expression is named Exp1 followed by a colon. Expressions can be renamed
by simply typing over Exp1 on the QBE grid. To use any object already listed (or previously
calculated) in the current query, save the query before writing the expression. By doing so, these
objects now become available to use in the Expression builder. When referring to fields already
selected on the QBE grid, the table names are not required in the formula unless the names are
ambiguous (i.e., several fields have the same name – this can occur when using multiple tables).
Placing this expression into the appropriate query we get the following:
Tables: Finances
Field
ID#
Table
Sort
Show
Criteria
total: [Finances]![dues-paid]+
[Finances]![donation]
Finances
x
x
id#
635
534
345
546
903
534
total
100
50
150
250
0
70
Figure 29 – Query 17
WRITING QUERIES WITH AGGREGATIONS AND EXPRESSIONS
Queries may become more and more complex as the many tools available are combined together.
Thus far queries have been used to select (filter) records using one or more sets of criteria, sort
records, aggregate data based on field groupings, and now perform calculations. In the following
query, both the aggregation of data and the use of expressions will be required.
Summarize for each member id the dues-paid, donations made, and total value of
their transactions. Remember that an individual member can make one or more financial
transactions. Thus to total these transactions the Aggregate function tools will be required. Once
these aggregated values are saved, the expression builder feature can be used to add SumofDuesPaid to SumofDonations.
This may be done in a single query or with the use of a previously written query such as the
previous query, which has already calculated the total dues plus donations and just requires
aggregation. The example below uses the one-step approach, both aggregating the data and then
applying the expression. Please note that not all questions can be answered in a single query. The
query tool first aggregates data and then does the calculation. In some instances the order of these
two operations may require opposite, first a calculation is required then the data needs to be
aggregated. In such cases the user will need to create two queries.
Page 19
Using Databases to Solve Problems
Tables: Finance
Field
ID#
Table
Total
Sort
Show
Criteria
Dues-Paid
Donation
Finances
Group by
Finances
Sum
Finances
Sum
Expression
x
x
x
x
id#
SumOfdues-paid SumOfdonation
345
100
50
534
100
20
546
0
250
635
100
0
903
0
0
total: [sumofdues-paid]
+[sumofdonation]
total
150
120
250
100
0
Figure 30 – Query 18
To execute this query it is best to create the query excluding the expression and then save
it. Only after it is saved will these values (SumofDues-Paid, SumOfDonations) be available for use
in the Expression Builder. Notice that the Total row contains the word Expression in the field
containing the formula. Whenever the total row is used (whenever there are aggregations) fields
containing calculations must include Expression.
Determine the amount still owed, assuming members are required to pay a total of
$100 in dues. To accomplish this, the information generated in the previous query will be
needed, specifically the sum of the dues paid by member. Thus a new query based on the results
of Query 18 will be constructed. The calculation required will be the $100 minus the SumOfDuesPaid
Tables: Query 18
Field
ID#
Table
Query18
Sort
Show
x
Criteria
dues owed: 100 – [Query18]![Sumofdues-paid]
Query18
x
Object used is a
previous Query
id#
345
534
546
635
903
owed
0
0
100
0
100
Figure 31 – Query 19
Notice that in Query 19, Query 18 was used instead of a table. It is permissible to use any
combination of tables and query objects to create new query objects. Note the syntax of the
expression in the second query. The expression is named dues owed. The formula subtracts the
previously calculated amount from a constant. Here the object identifies the data source as
[Query18]! with a table name it is followed by an exclamation point. The field name is
[Sumofdues-paid] (since the dues-paid field was summed in Query 18, the resulting field in the
Query 18 dynaset is named Sumofdues-paid).
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Using Databases to Solve Problems
NULL VALUES:
Consider the original finances table. When a member makes a dues payment without a donation,
a zero has been entered in the donation field. But what if that field is left blank as seen on the
modified table in Figure 32? These blank fields in a record are known as null values.
Original Table:
Modified Table with Null Values:
ID
Dues-Paid
Donation
635
534
345
546
903
100
50
100
0
0
0
0
50
250
0
ID
635
534
345
546
903
Dues-Paid
100
50
100
0
Donation
50
250
Figure 32
Figure 33
In Excel, blank cells are considered to be 0 when they are added. For example, the result of the
expression A1+B1, where cell A1 is blank (null) and cell B1 contains 10, is the value 10. Excel’s
algorithm for dealing with a blank cell in addition is to ignore it. In Access however, these null
values are treated differently. In a calculated field of a query with the formula [sumofduespaid] +[sumofdonation], if the donation amount is null for a specific record, the value
returned will be null for that record.
This propagation of null values can often lead to incorrect results. Let’s consider the affect this
modified table would have on the QBE grid from query 17 that is designed to calculate total
transaction value (dues+donation). Observe that the total value for the first record is null. The
computer performs the calculation 100 + null which results in a null value. So even though
member 645 made a $100 payment the total value displayed is null.
Query 17-modified - Tables: Modified Finances
Field
ID#
Table
Sort
Show
Criteria
Finances
x
total: [Finances]![dues-paid]+
[Finances]![donation]
x
id#
635
534
345
546
903
534
total
150
70
Figure 34
Page 21
Using Databases to Solve Problems
Obviously this poses the problem of how to obtain an accurate subtotal of each financial
transaction. One of the easiest ways to work with fields that may contain null values is to use the
Nz function. The Nz function works like an IF statement. It takes a value in a field and if the
value is null, it substitutes an alternate value. If the value is not null, it simply returns the original
value. The value substituted for the null value can be user defined, or in the absence of a user
definition it will default to zero.
Nz ([variant], valueifnull)
Here is the modified query using this Nz function in the calculated field expression as follows:
Field
ID#
Table
Sort
Show
Criteria
Finances
x
total: Nz([Finances]![dues-paid])+
Nz([Finances]![donation])
x
id#
635
534
345
546
903
534
total
100
50
150
250
0
70
Figure 35
The expression used total: Nz([Finances]![dues-paid]) + Nz([Finances]![donation])
places the Nz function in front of each operand. Since a value if null is not given, a field containing
a null value will result in the value zero. The computer will then interpret this as follows for the
first record (id 635) of the Finances table: Nz(100) + Nz( null)  100 + 0  100.
Page 22
Using Databases to Solve Problems
EXERCISE 9.1 EMPLOYEE DATABASE
The following Access tables represent staff utilization for an ad agency. Each record in the Jobs1
and Jobs2 tables represents a task performed for that job. Answer the questions in this problem
based on the tables below. You will be asked to list all tables required to complete each query.
Table: Job1
taskid# Employee# Minutes
1
1
23
2
3
13
3
4
17
4
3
5
5
3
15
6
8
8
7
7
5
8
1
12
9
7
6
Date
7 /3 /2006
7 /3 /2006
7 /8 /2006
7 /9 /2006
7 /10/2006
7 /10/2006
7 /10/2006
7 /12/2006
7 /13/2006
Table: Employees
Employee#
Name
Job Description Job Rate
1 Jorenson,Mike
Artist II
$42.50
2 Howsworth,Elizabeth Editor
$32.75
3 Rancine, Michael
Photgraher
$55.00
4 Elkins, Naomi
Artist II
$44.50
5 Waters, Ann Marie
Artist I
$27.50
6 Devons, Robert
Senior Editor
$52.80
7 James, Miranda
Artist II
$42.50
8 Ballack, Stephanie
Editor
$37.20
9 Moreno, Mandy
Ad Exec
$125.00
Table: Job2
taskid# Employee# Minutes
1
3
20
2
4
10
3
1
15
4
3
5
5
3
15
6
9
12
7
7
22
8
7
15
1. (a) Draw the relationship diagram between these 3 tables. Label each primary key and
the foreign keys on your relationship diagram.
Table Name:
Job1
Primary Key:
Table Name:
Employees
Primary Key:
Table Name:
Job2
Primary Key:
(b) Why can’t employee# be the primary key on the Job1 table?
Page 23
Date
7 /1 /2006
7 /3 /2006
7 /3 /2006
7 /5 /2006
7 /9 /2006
7 /9 /2006
7 /10/2006
7 /11/2006
Using Databases to Solve Problems
2. Design a query to list for each Job2 task the following information: the taskid#, employee’s id
and minutes they worked on this task.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
3. Design a query to list the taskid# and employee’s id for each Job1 task which lasted at least 15
minutes.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 24
Using Databases to Solve Problems
4. Design a query to list the employee id number for employees who worked on Job2 on either
July 1, 2006 or on July 10, 2006.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
5. Design a query that lists the employee’s id and date and minutes spent for the Job 1 tasks that
were between 15 and 20 minutes long (inclusive).
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 25
Using Databases to Solve Problems
6. Using the Access Query design view below, design a query that results in a list of employees
(Employee#) who worked on Job1 who:


Worked for more than 10 minutes on a task on or after July 10, 2006 or
Worked at least 5 minutes on a task before July 10, 2006.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
7. Using the Access Query design view below, design a query that will result in a list of all
employees whose last names begin with the letter M or N.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 26
Using Databases to Solve Problems
8. Using the Access Query design view below, design a query to list the names of each employee in
alphabetical order.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
9. Using the Access Query design view below, design a query to list the Employees who earn more
than $35 per hour (job rate). List each employee’s name, Empoyee#, and Job Rate. Sort your list
by Job Rate (most expensive first) and then alphabetically by name.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 27
Using Databases to Solve Problems
10. Design a query summarizing the Job2 tasks by employee. The list should include Employee#
and the total minutes worked by that employee.
Tables __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
11. Design a query summarizing the Job1 tasks by employee#. The list should include Employee#,
the number of tasks they worked, and the average time per task that they worked.
Tables __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 28
Using Databases to Solve Problems
12. An overhead fee of $5 per task is assessed for each task regardless of duration. Using the
result from the previous query (which you named query11), write a query in the design view below
which will return the Employee#, and the total amount of overhead fees for this employee for
Job1. If an employee has not worked their name should not appear on this list.
Tables __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Additional room for calculated expression if needed:
Page 29
Using Databases to Solve Problems
13. Currently clients are billed the cost of the tasks completed (hourly rate times hours) plus the
overhead fee assessment. An alternative method of billing overhead has been suggested by
management as follows: Hourly overhead costs will be billed at 25% of the hourly wage plus $3
per hour. So an Ad Exec with an hourly wage of $125/hour would have an hourly overhead charge
of $125*.25 +3. Write a query to calculate the hourly overhead charge for each of the different
employees listed on the employees table. If the Job Rate field is blank the overhead charge should
simply be $3.
Table __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Additional room for calculated expression if needed:
Page 30
Using Databases to Solve Problems
EXERCISE 9.2 CHAPTER REVIEW – LIBRARY DATABASE
The tables below represent the database system for the Fergie Library. The Book table lists the
names of all the books and periodicals owned by the library. The Cardholder table lists the names
of all authorized library users. The Circulation table is a running list of books that are borrowed.
When books are borrowed, they are entered onto this table, and when they are returned, the
original entry is noted as returned.
Books
Book#
23456
834592
4539
33982
33983
43928
Title
1812
Gone With the Wind
Webster’s Unabridged Dictionary
Hunt for Red October
Hunt for Red October
Joy of Cooking – 5th Edition
Circulation
Borrow#
A83765
A83765
C52938
C77328
Cardholders
Borrower#
A23457
C52938
A83765
Book#
4539
33982
4539
43928
Date Borrowed
7/1/98
7/1/98
7/4/98
7/6/98
LastName
Smith
Jones
Walters
FirstName
Michael
Jennifer
John
Author
Vidal
Mitchell
Webster
Clancy
Clancy
Smith
Type
4
4
3
1
1
2
Price
$39
$19
$86
$22
$22
$45
Returned
Yes
No
No
Yes
Address
th
222 East 7 ST
18 Main Street
55 Elm Street
City
State
Zipcode
Bexley
Dublin
Columbus
OH
OH
OH
43209
43218
43213
1. Database Relationships. Set up the relationships of this database. Using the boxes below, fill in
the primary key (if any) of each table and draw relationship lines between tables. Label each
relationship with the name of the foreign key(s).
Table name:
Books
Primary Key:
Table name:
Circulation
Primary Key:
Table name:
Cardholders
Primary Key:
Page 31
Using Databases to Solve Problems
2. What field type (Text, Number, Currency, Date/Time, Yes/No, AutoNumber) is best suited for
each of the following fields:
Borrow# (Circulation Table)
_______________________
Date Borrowed (Circulation Table)
_______________________
Returned (Circulation Table)
_______________________
Address (Cardholders Table)
_______________________
3. Using the query design view below, construct a query to list the book titles and authors of all
the type 4 books in alphabetical order by author then by book.
Tables Used _____________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
4. List the dynaset created from the query in question #3 based solely on the data shown.
Page 32
Using Databases to Solve Problems
5. List the title of all books that begin with the letters G or J.
Tables Used _____________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
6. List the book# and borrow# of all books borrowed between June 1, 1998, and July 4, 1998.
Sort the list by the borrower’s number.
Tables Used ____________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 33
Using Databases to Solve Problems
7. List the title of all books that are either type 1 and cost less than $25 or type 2 and cost less
than $50.
Tables Used __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
8. Write a query that will summarize the books by author. The query should list the author’s
name, the total number of books in the collection by that author, and the average price of that
author’s books.
Tables Used __________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Page 34
Using Databases to Solve Problems
9. The library would like to calculate the accrued fines for lost books. You will assume that all
books borrowed before January 1, 2001 and not returned are lost. The following fine is
charged for all lost books: $.05 per day from the date borrowed plus a $10 flat fee handling
charge. For each lost book, list the book number, the borrower number, and the fine.
Tables Used ___________________________________
Field
Table
Total
Sort
Show
Criteria
OR
OR
Additional Expressions:
Page 35