DAY 16:
ACCESS CHAPTER 2
Tazin Afrin
Tazin.Afrin@mail.wvu.edu
October 10, 2013
1
OBJECTIVES
• Single table query
• Multi-table query
2
SINGLE TABLE QUERIES
• Which customer currently has a balance
over $5000?
– Create a query
• A query enables you to ask questions
about the data stored in a database.
• Need reference of table
– For previous question refer Account table
3
QUERY DESIGN VIEW
• Query Design view enables you to create
queries; the Design view is divided into
two parts –
– the top portion displays the tables
– the bottom portion (known as the query
design grid) displays the fields and the
criteria.
4
SINGLE TABLE QUERY
• Create in two ways –
– Simple query wizard:
• provides dialog boxes to guide you through the
query design process.
• helpful for users who are not experienced.
– Query design tool:
• For more advanced users
• Provides the most flexibility
5
QUERY DATASHEET
• Display the results of the query.
• Query’s datasheet looks and acts like a table’s
datasheet
• Usually a subset of the records from the table.
• Only shows the records that match the criteria.
• Allows you to enter a new record, modify an
existing record, or delete a record.
• Any changes made in Datasheet view are
reflected in the underlying table.
• Caution: Changes Made to Query Results
Overwrite Table Data
6
SINGLE – TABLE SELECT QUERY
• A select query displays only the records
that match the criteria entered in Design
view.
• Create -> Queries -> Query Design
• Show Table Dialog Box appears
• Select table
• Add query
7
USE QUERY DESIGN VIEW
• Consists of two parts:
– The top portion contains tables with their
respective field names.
– The bottom portion (known as the query
design grid) contains columns and rows.
•
•
•
•
•
Field row
Table row
Sort row
Show row
Criteria row
8
WILDCARD
• A wildcard is a special character that can
represent one or more characters in the
criterion of a query.
• * mark
– Represents one or more characters
– If name start with Sm search by Sm*
– S*nd will return Sand, Stand, or StoryLand.
• ? mark
– Stand for a single character
– H?ll will return Hull, Hill, or Hall etc.
9
COMPARISON OPERATORS
• A comparison operator can be used in the
criteria of a query.
• Such as –
–
–
–
–
–
–
equal (=)
not equal (<>),
greater than (>)
less than (<)
greater than or equal to (>=)
and less than or equal to (<=)
• Query for salary >5000
10
NULL
• Null is the term Access uses to describe a
blank field.
• Example:
– Is Null
• For an Employee field in the Customers table
when the customer has not been assigned a sales
representative.
– Is Not Null
• For the ShipDate field; a value inserted indicates
the order was shipped to the customer.
11
ESTABLISH LOGICAL CRITERIA
• The AND logical operator returns only
records that meet all criteria.
• The OR logical operator returns records
meeting any of the specified criteria.
• The NOT logical operator returns all
records except the specified criteria.
12
QUERY OPERATION
• Copy a query
• Run a query
13
MULTI-TABLE QUERY
• A multi-table query contains two or more
tables.
• Enables you to take advantage of the
relationships that have been set in your
database.
• Related tables should already be established
when you create a multi-table query.
– Related tables are tables that are joined in a
relationship using a common field.
14
MORE OPERATIONS
•
•
•
•
Add additional tables
Get answers using query
Modify multi-table query
Add and delete fields
15
COMMON MISTAKE
• Use tables in query who are not joined.
– Results in more rows than usual
– For example, If we create a query on Customer table
and Branch table but forget to join them.
– Suppose Customers table contains 11 records, and
the Branch table contains 5 records.
– Since Access does not know how to interpret the
unrelated tables, the results will show 55 records –
every possible combination of customer and branch
(11*5).
• When add new table, create relationships.
• Temporary join line in query will not create an
actual join line between tables.
16
NEXT CLASS
• Access Chapter 3
– Order of operations.
– Create a calculated field.
– Create expressions.
– Use built-in functions.
– Perform date arithmetic.
17
THANK YOU
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