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Temporary tables are useful when you need to do something on the fly. Instead of writing full CREATE TABLE statement and then inserting from another table, you can do the following with one query:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
Example:...

Before creating a swap file, we should check the size of the current swap:
#cat /proc/meminfo | grep SwapTotal
SwapTotal: 9233400 kB

If you want to add cronjob or edit an existing one you can use the crontab command:
#crontab -e
The '-e' param stands for edit. This will open the crontab file for the current logged user. If you want to edit the crontab file for a specific user you need to specify the username:...

Sometimes mysql may not use the index you created for some reason. To force mysql to use an index you can use FORCE INDEX.
| FORCE {INDEX|KEY}
[FOR {JOIN|ORDER BY|GROUP BY}] (index_list)