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 fieldyou 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  QueryDesign.  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  clickBrowse 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.