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It's a very powerful feature and a fundamental part of relational databases since you can remove multiple records at one time, and can specify which records to delete by linking to data in another table. Understanding and using Delete Queries improves the performance of your applications versus doing the same changes manually or in code , and makes them easier to maintain.

When you use a DELETE query, only the data is deleted; the table structure and all of the table properties, such as field attributes and indexes, remain intact. Cascade delete operations cause the records in tables that are on the many side of the relationship to be deleted when the corresponding record in the one side of the relationship is deleted in the query. For example, in the relationship between the Customers and Orders tables, the Customers table is on the one side and the Orders table is on the many side of the relationship.

Deleting a record from Customers results in the corresponding Orders records being deleted if the cascade delete option is specified. If you want to delete values in a specific field, create an update query that changes the values to Null. It's one thing to delete trivial data or records from a temporary table. It's quite another for deleting historic records from a table to save space or thinking that the old data is never going to be used again.

Disk space is quite cheap and trying to get those records back could be very expensive or impossible if there are no backups. If the records are part of referential integrity with cascading deletes, lots of data could be lost.

An alternative to deleting records is simply tagging them as old. You can then reference that field when you don't want to include them in your selections. This preserves the records in their original table so you can perform analysis on them in the future. There may be situations where the amount of data is so large that records should be deleted for performance or database size reasons.

In this case assuming you can't migrate to SQL Server , you should at least archive the old data rather than deleting them permanently.

Simply create an empty copy of your table, insert the old records into that, then delete them from your original table. If there are related records linked through cascading deletes, you'll want to archive those records before deleting the main records. In this example, the records in a call list are deleted if they placed an order and got added to the customer list with their CallListID:.

Simply open the table and manually try to edit a field or delete a record you expect to eliminate. If you can't do it manually, the query can't make the deletions either.

This can be due to several reasons:. Assuming you can delete records from your table, your query may fail and display a "Could not delete from the specified tables" error message when you run it:. Delete Query Error: Could not delete from the specified tables. This error appears when the table is linked to another table's fields, and the linked field s is not the primary key.

Access interprets the link as not representing a one-to-one relationship, and prevents deletions. It simply fails to run. For instance, you may want to delete people from TableA who are in TableB by linking their name fields both tables have another field as its primary key :. This setting can also be set from the query's Property Sheet when editing the query in Design View.

Simply set the Unique Records property to Yes:. If you are interested in deleting a table, use the DROP syntax:. They are extremely powerful, fast, and eliminate manually deleting records and writing unnecessary code. They are also much easier to maintain and debug than module code.

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Other Products. Sentinel Visualizer. Total ZipCode Database. All Products: Demos, Catalog, Awards, etc. All Products. Product Awards. Forum and Ticket Submissions. Support Options. Product Updates. From the Access designer, you can interactively create a query and specify its type: Delete Query Option when Designing Queries in MS Access and Delete Query Option when Designing Queries in MS Access and Delete Queries let you: Empty a table delete all its records Delete all records with a particular value in a field Delete all records with a range of values in a field Delete records based on criteria in multiple fields Delete records with matching values field s in a joined table.

Only records that satisfy the expression are deleted. Remarks When you use a DELETE query, only the data is deleted; the table structure and all of the table properties, such as field attributes and indexes, remain intact.

Important After you remove records using a delete query, you cannot undo the operation. If you want to know which records were deleted, first examine the results of a select query that uses the same criteria, and then run the delete query. Maintain backup copies of your data at all times. If you delete the wrong records, you can retrieve them from your backup copy. Avoid Deleting Historic Data.

Store Historic Records in an Archive Table There may be situations where the amount of data is so large that records should be deleted for performance or database size reasons. Delete Query Examples. Delete Query Fails to Run. Do You have Rights to Delete Records? This can be due to several reasons: The database file is set to Read-only. None of the data can be modified.

Change this at the Windows level. If the database is on a CD, copy it to your hard disk. If you're using Access workgroup security, you may not have rights to delete the data. In this case, login as the administrator or with a user name and password that gives you the appropriate rights.

If the tables is linked, you may not have rights to modify the data with the backend data source. Query Fails with This Message: "Could not delete from the specified tables" Assuming you can delete records from your table, your query may fail and display a "Could not delete from the specified tables" error message when you run it: Delete Query Error: Could not delete from the specified tables This error appears when the table is linked to another table's fields, and the linked field s is not the primary key.

Name Unfortunately, the query triggers the warning message when you try to run it. Name This setting can also be set from the query's Property Sheet when editing the query in Design View.

Deleting a Table with the Drop Syntax. Hope this helps! News Features. Microsoft Access Query Center.

 

Microsoft access 2013 vba programming free

 

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