[MySQL] Deleting/Updating Rows Common To 2 Tables – Speed And Slave Lag Considerations
Introduction
A question I recently saw on Stack Overflow titled Faster way to delete matching [database] rows? prompted me to organize my thoughts and observations on the subject and quickly jot them down here.
Here is the brief description of the task: say, you have 2 MySQL tables a and b. The tables contain the same type of data, for example log entries. Now you want to delete all or a subset of the entries in table a that exist in table b.
Solutions Suggested By Others
DELETE FROM a WHERE EXISTS (SELECT b.id FROM b WHERE b.id = a.id);
DELETE a FROM a INNER JOIN b on a.id=b.id;
How To Delete All Messages From A Folder In Pine
Pine is a UNIX command line mail application. So how do you delete all messages in a folder?
The combination is
1 | ; A A D |
If after pressing ; you see
1 | [Command ";" not defined for this screen. Use ? for help] |
then you don't have a check in the "Enable aggregate command set" settings checkbox. To enable it, go to the main menu (M) -> Setup (S) -> Config (C) and scroll down to "Enable aggregate command set". Then press X (to check it), E (Exit). Now repeat the above.
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