Is there an efficient way to get the list of affected row IDs (not the # of affected rows via PHP's mysql_affected_rows(), but the actual row ids that were affected) from an UPDATE or DELETE query in mysql?
In postgresql, there is a RETURNING clause within UPDATE/DELETE queries that can be used to specify values from the affected rows that are returned.
In mysql, the 'brute force' way of getting the affected rows seem to be: 1. Acquire READ LOCK. 2. SELECT to with the WHERE condition of the UPDATE/DELETE query to get the affected row ids. 3. UPDATE/DELETE. 4. RELEASE LOCK.
The above way seems very inefficient. Is there a more efficient way to get the affected row ids in mysql?
You can create a Trigger
Support for triggers is included beginning with MySQL 5.0.2. A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table.
the following code creates a trigger on a table named
mytable which has a field
CREATE TRIGGER mytable_delete AFTER DELETE ON mytable FOR EACH ROW SET @deletedIDs = CONCAT_WS(',', @deletedIDs, OLD.id)
OLD refers to deleted row
once you created a trigger on a table you can use it as follows:
/* empty parameter defined in CREATE TRIGGER */ Set @deletedIDs = ''; /* perform your query */ DELETE FROM mytable WHERE myotherfield = 'myfilterevalue'; /* get the parameter */ SELECT @deletedIDs AS 'Deleted_IDs';
this will return deleted IDs each preceded by a comma in a string
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