1. Chapter 9 - Action Queries
Access
Chapter 9 - Action Queries

2. Queries
What can be accomplished with queries is only limited by your skills and imagination
The more you learn about defining criteria and creating expressions, the more you can do with these queries
PgP MIS 342 Access

3. Action Queries Warning-These Queries Modify Data!
Have a backup .mdb or .accdb file!
These queries illustrate why many corporate DBA’s do not want employees using Access!
Instead, they prefer programs like Business Object’s Crystal Reports
Why?
PgP MIS 342 Access

4. Action Query Tip Create Select query first
Make sure criteria is selecting correct record set
Then convert to Action Query
PgP MIS 342 Access

5. Make-Table Query Create new table from tables or queries
Use to create temporary tables
Use to create snapshots of data at certain points in time
PgP MIS 342 Access

6. Update Query Change values of fields that meet certain criteria
PgP MIS 342 Access

7. History Table (Append/Delete)
Applications often use two tables
Current Table, records for current accounting period
History Table, records from prior accounting periods
PgP MIS 342 Access

8. History Table (Append/Delete)
Why use two tables?
Current Table will have fewer records, improve application performance
History Table records generally not accessed as often
If History is too old, may create Archive table
PgP MIS 342 Access

9. History Table (Append/Delete)
How created?
Append desired Current Table records to History Table with Append Query
Delete same records from the Current Table with Delete Query
PgP MIS 342 Access

10. Relationships One to many Many to many One to one
Entity subtypes (billing address differs from shipping address, or security issues, such as employee info)
PgP MIS 342 Access

11. Indexes Pro: Con: Speeds search of records in queries
Adds to disk storage requirements
Takes time/CPU cycles to create and maintain
PgP MIS 342 Access

12. Joins Inner Join: Outer Join, left or right: Self-join
Same value in common field
Outer Join, left or right:
All records from first table, only records from second table with matching common field
Self-join
Join table to copy of itself
PgP MIS 342 Access