Microsoft Access – Tutorial 3
Querying a Database
 a query is a question you ask about data stored in a
database
 you tell Access what fields you need and what criteria
Access should use to select the records
ex. find records for employers located in a specific State or
Province
 queries allow you to:
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display selected fields and records from a table
sort records
perform calculations
generate data for forms, reports and other queries
update data in the tables in a database
find and display data from two or more tables
Microsoft Access – Tutorial 3
Query by Example (QBE)
 We use the Query Window in Design View to create a query
 You Query by Example by giving Access an example of the
information we are requesting
 Access then retrieves the information we are requesting
 We want to create a query to display:
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employer ID
employer name
city
contact first name
contact last name
web site information
for each record in the Employer table
Microsoft Access – Tutorial 3
Query by Example (QBE)
 open the Northeast database we created last week
(I have included a copy in the Common Directory on the
desktop)
 Click Queries in the Objects bar
 click the New button
 make sure Design View is selected and click OK
 show the Employer Table and the close the Show Table
dialog box
 maximize the Select Query window
Microsoft Access – Tutorial 3
Query by Example (QBE)
 you will see the field list in a box entitled Employer (the
table name)
 you can double-click or drag fields to the design grid
 in the design grid, you include the fields and record selection
criteria for the information that you want to see
 you can see the current results of your query at any time by
View button or the Run button on the Query Design
toolbar
 the current results will appear in a datasheet view
Microsoft Access – Tutorial 3
Query by Example (QBE)
 drag the split bar and resize the windows as you like
 double-click the following fields in order: EmployerID,
EmpoyerName, City, ContactFirstName, ContactLastName
and Website
 note the checkbox that that allows you to show or hide fields
 click Run (or View (Datasheet View)) to see the results in a
datasheet
 click the View button to return to Design View
 click the Save button on the toolbar and name the query
EmployerAnalysis
Microsoft Access – Tutorial 3
Updating Data using a Query
 return to the Datasheet view
 indicate that The Adele Bannister House (10135) now has a
website
 change the Contact person for Alpine Touring Center
(10152) to Mary Grant
 close the Query and note that it has been added to the
Queries in the Objects bar
 open the Employers table and verify that the changes have
been made
 close the Employers table
Microsoft Access – Tutorial 3
Table Relationships
 remember that Access is a relational database management
system
 relationships are created among tables by using common
fields
 this process is often called a join
 when you join tables with a common field, you can extract
data from them as if they were one table
 the Employer and Position tables are joined with the
common field EmployerID (a foreign key)
 you can use a query form or report to extract selected data
from each table even though the information is in two tables
Microsoft Access – Tutorial 3
One-to-Many Relationships
 a one-to-many relationship exists between two tables when
one record in the first table matches zero, one or many
records in the related table
 and when one record in the in the second table matches
exactly one record in the first table
 the primary table is the one table in the one-to-many
relationship
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this is the Employer table
the related table is the many table
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this is the Position table
Microsoft Access – Tutorial 3
One-to-Many Relationships
 orphaned records can be created when inconsistencies
occur between tables
 for example:
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if an Employer ID is changed in the Employer table
if an Employer is deleted from the Employer table
if a position is added for an Employer that doesn’t exist in the
Employer table
Microsoft Access – Tutorial 3
One-to-Many Relationships
 Referential Integrity is a set of rules that Access uses to
prevent records from being orphaned
 it maintains consistency between tables when you update
data
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when you add a record to a related table, a matching record
must already exist in the primary table
if you attempt to change the value of a primary key in the
primary table, Access prevents the change if matching records
exist in a related table
(however, if the cascade updates option is chosen, the
foreing key values will be updated automatically)
Access prevents the deletion of records in a primary table if
matching records exist in a related table
(if cascade deletes option is selected all records with that key
will be deleted – this is not recommended)
Microsoft Access – Tutorial 3
Defining Relationships
 you can define relationships between tables using the
Relationships window
 click the Relationships button on the Database toolbar
 add Employer and AvailablePositions and close the Show
Table dialog box
 lengthen and widen each window to show all fields
 click and drag EmployerID from the Employer Table to
EmployerID in the AvailablePositions table
 the Edit Relationships window will appear
 the Primary Table, Related Table and Common Field will be
visible
Microsoft Access – Tutorial 3
Defining Relationships
 check Enforce Referential Integrity
 note that the two Cascade options become available
 check Cascade Update Related Fields
(remember that it is not recommended to check the Cascade
Delete Related Records as you may inadvertently delete
records)
 click create and note the join line that appears and the
symbols on it
now create a one-to-many relationship between the NAICS
table and Employer Table with NAICS code as the common
field (foreign key)
 click the Save button and Close the window
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Microsoft Access – Tutorial 3
Multi-Table Queries
 now that we have created Relationships among (joined) our
tables, we can query them as one
 create a new query in design view
 add the Employer and PositionsAvailable tables
 create a query in the following order:
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EmployerName
City
StateProv
Openings
PositionTitle
StartDate
EndDate
run it and save the query as EmployerPositions
Microsoft Access – Tutorial 3
Sorting Data in a Query
 sorting is rearranging records in a specified order or
sequence
 open the EmployerPositions query in datasheet view
 select the first record in the Employer Name field and use
the sort buttons to sort alphabetically
 to sort by more than one field go to Design View
 select the entire column for Openings
 click and drag it so that it is the last field (after EndDate)
 use the Sort field to sort PositionTitle Ascending
 sort Openings Descending
 run the query
 within groups of fields with the same Position Title, the
record – save the query
Microsoft Access – Tutorial 3
Filtering Data in a Query
 you can filter query results using the Filter by Selection
button
 double-click the word clerk in one of the Position Title
records
 click the Filter by Selection button and you will see only
results for different kinds of clerks
 click the remove filter button to turn off the filter
 filter results for New Hampshire (NH)
Microsoft Access – Tutorial 3
Defining Record Selection Criteria
 you can specify a condition which is a criteria or rule that
tells Access which records to display
 we will create query by using wizard using a condition
 click create query by using wizard and make sure the
Table: AvailablePositions is selected
 add all the fields by clicking >>
 remove both PositionID and EmployerID from the Selected
Fields list box
 to add fields from another table after the current set of fields,
select Openings
 now add EmployerName, StateProv, ContactFirstName,
ContactLastName and Phone from the Employer Table
Microsoft Access – Tutorial 3
Defining Record Selection Criteria
 click the Next button
 make sure the Detail radio button is selected and click Next
again
 name the Query July1Positions and click the Modify the
Query Design radio button
 in the StartDate Criteria type 07/01/2006
 Access adds # signs before and after the criteria
 run and save the query
 only positions with start dates of July 1st will be displayed
Microsoft Access – Tutorial 3
Formatting the Appearance of the sheet
 select all the records
 Format>Font
 change the size of the fonts to 8
 double click between columns to resize them
Microsoft Access – Tutorial 3
Setting Range Criteria
 open the July1Positions query in Design View
 remove the Start Date criteria
 set the Wage criteria >=17
 run the query and Save it As HighWageAmounts
Microsoft Access – Tutorial 3
Using Multiple Selection Criteria with the And operator
 open the July1Positions query in Design View
 add PE as criteria for StateProv
 run the Query and you’ll see results that match both criteria
 close and save the query
 right click on the Query July1Positions in the Query window
 rename it PEJuly1Positions
Microsoft Access – Tutorial 3
Using Multiple Selection Criteria with the Or operator
 create a new query in Design view
 use the Employer and AvailablePositions tables and add the
following fields: EmployerName, City, PositionTitle,
HoursPerWeek, and Experience
 set the HoursPerWeek criteria to <30
 in order to select records in which either (not both) of the
conditions is met type Yes in the or: field
 run the query
 sort it alphabetically ascending by Employer Name
 Save it as HoursorExperience