actions queries

Actions Queries
Understanding Action Queries

Action queries are a way to make corrections to
database. They can make an enormous mess of
database if used incorrectly.

Action queries differ from select queries:
−
A select query shows you data that meet your
criteria.
−
An action query looks for the data that meets
your criteria, and then does something with it,
such as making changes to the data or moving
records to a new table.
Testing Action Queries (Carefully)

Most importantly, before you use an action
query, make a database backup! because it may
not always generate the result you expect (mong
đợi).

To make a backup, you can copy your .accdb
database file or File Save & Publish to enter ➝
Backstage view, look in the Advanced section of
the Save Database As list Back Up Database.
The Action Query Family

An update query changes the values in one or
more records.


An append query selects one or more records,
and then adds them to an existing table.

A make-table query selects one or more records,
and then creates a new table for them.

A delete query deletes one or more records.
Update Queries

An update query searches for some records and
then modifies them.

Using the update query when you work on lots of
data or when you want to update multiple fields.

Update query makes to change multiple records
at same time.
Update Queries

To Create a Update Query:
−
Select Create tab  Queries  Query Design.
−
Add each table you want to include in query by
selecting it and then clicking Add.
−
Change query to an update query by choosing
Query Tools  Design  Query Type 
Update.

−
Add the field you want to use for filtering,
and then set the Criteria box for each one.
Update Queries
−
Add the field you want to change.
−
In the Update To box, supply the new value that
your query will apply to each field.
Update Queries
−
Add any other fields that you want to inspect to
confirm that you’re selecting the correct
records.
−
Right-click the query’s tab title, and choose
Datasheet View to see the rows that query
affects.
−
Now switch back to Design view, choose Query
Tools  Design  Results Run to run update
query and have Access apply your changes.
Update Queries

Access warns you about the change it’s about to
make. Click Yes to make the change.

If you want to save your query, then press Ctrl+S
You’ll need to supply a name for your query.
Append Queries


An append query selects records from a table
and then inserts them into the end another table.

You may want to use an append query to
transfer records from one database to another.
This technique is handy if you have duplicate
tables in different databases.

To transfer the records, you need to make sure
the two tables line up. (Page 255)
Append Queries

Create a new query by choosing Create
Queries  Query Design.

Using the Show Table dialog box, add the source
table that has the records you want to copy.

Query Tools Design Query Type Append.➝ ➝
Append Queries
−
Another Database: transfer the records to
another database click Browse to select
database file OK.
−
Table Name box: enter the name of the table to
which you want to transfer the records.
−
Click OK to close the Append or Make Table

dialog box.
−
Add the field you want to copy from the source
table.
Append Queries
−
If you’re creating an append query, then fill in
the names of the destination fields in the
Append To boxes.
−
If want to copy only some of the records in the
source table, then set the filter conditions you
need.
−
Choose Datasheet View to see the rows that
your query affects.
Append Queries
−
Switch back to Design view, and then choose
Query Tools Design  Results  Run to
transfer your records.
−
Press Ctrl+S to save query.
Make-Table Query

The make-table query creates the destination
table, and then copies the records to it.
−
Open the source database.
−

Choosing Create Queries Query Design.➝ ➝
−
Add the source table that has the records you
want to copy.
−
Select Query Tools Design Query Type ➝ ➝ ➝
Make Table.
Make-Table Query
−
Another database: transfer the records to another
Database, click Browse to select database file  OK.
−
Table Name: enter the name of the table which you
want to transfer the records.
Make-Table Query
−
Add the field you want to copy from the source
table.
−
To copy only some of the records in the source
table, then set the filter conditions.
−
Choose Datasheet View to see the rows that
your query affects.
−
Switch back to Design view  Results Run to ➝
transfer the records.
−
Press Ctrl + S to save query.
Delete Queries


Delete queries are the simplest and most
dangerous of the action queries.

Delete query erases records from the database.

To create a delete query:
−
Select Create tab Queries Query Design.➝ ➝
−
Add the table that has the records you want to
delete.
−
Select Query Tools Design Query Type ➝ ➝
Delete.
Delete Queries
−
Add the fields you want to use for filtering, and
then set filter conditions.
−
Add the fields that you want to inspect to confirm
you’re getting the correct records in the datasheet
view.
−
Choose Datasheet View to see the rows that’ll be
affected by query.
−
Switch back to Design view, choose Query Tools 
Design  Results  Run to remove the records.