Writing a delete query in access
Access delete query sql
Click OK, close the Relationships pane, and then go on to the next set of steps. Drag the LastName field from the tblEmployees field list into the design grid. Otherwise, the update query sets to NULL every record in each of the fields in your query. Let's run the delete query and delete the selected records. In our scenario, we only wish to keep records in the table where the student is still currently active. If you want to delete records from multiple tablesfor example, a customer and all of that customer's ordersyou need to do a few things first: Define relationships between the tables. Things to verify before you use a query to delete any data Make sure that the file is not a read-only file: Right-click Start and click Open Windows Explorer. Add the tblCustomerTours table and tblTours table to the query. Remember that the delete query will permanently remove records from the specified table s , therefore it is very important that you have either appended your data to an archive table, or have backed up the table s or database. When you delete records on the "one" side of the relationship, you also delete all of the related records on the "many" side of the relationship. Click Yes.
This can be due to several reasons: The database file is set to Read-only. The Edit Relationship dialog box appears.
Writing a delete query in access
This can be due to several reasons: The database file is set to Read-only. If the database is on a CD, copy it to your hard disk. To revert to a backup, close and rename the original file so that the backup copy can use the name of the original version. Also, Access automatically enforces a set of rules called referential integrity. Maintain backup copies of your data at all times. It simply fails to run. Click the LastName column's Criteria row and type Chang. You will now see the the query design includes a new row labeled Delete, which allows you to specify a criteria to which the data will be deleted. Unless you want the query to delete each and every record in the tblCustomerTours table, you will need to add some limiting criteria. In this case, login as the administrator or with a user name and password that gives you the appropriate rights. If you wish to use the delete query to remove records from multiple tables rather than just a single database table, you will need to ensure that: You have relationships defined between related tables in your Microsoft Access database You have enforced the Referential Integrity for the relationships between your chosen tables.
Once in design view, we change the query type using the Query Type button on the toolbar. If this is the case, you must delete the records from the many side of the relationship first to ensure against orphaning recordsand then delete the records from the one side of the relationship.
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To allow us to append records to an archive table, we must first have the archive table created, whether it be in the active database or in another database. In our example we have an archived table created, named tblExpiredStudents, which will hold the historical records of students whose two years have expired.
This time Where appears in the Delete cell for the LastName field, indicating that the LastName field will be used as the criteria to select which records will be deleted from the tblCustomerTours table.
To create a delete query: in the database window, click the queries icon in the objects bar and click the new button. Access converts the select query to a delete query and displays the Delete row in the query design grid.
These rules ensure that the foreign keys in a database contain the correct values.
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