Question

I want to find the most recent edit date for tables in my database.

This is an example of the query I plan to use:

      SELECT `edited` FROM `table1`
UNION SELECT `edited` FROM `table2`
UNION SELECT `edited` FROM `table3`
UNION SELECT `edited` FROM `table4`
ORDER BY `edited` DESC
LIMIT 1

It works, but I am hoping someone can provide a more performant solution.

Answer 1

This may run faster as it will limit each of the selects to one row instead of returning all rows from each table.

      SELECT MAX(`edited`) FROM `table1`
UNION SELECT MAX(`edited`) FROM `table2`
UNION SELECT MAX(`edited`) FROM `table3`
UNION SELECT MAX(`edited`) FROM `table4`
ORDER BY `edited` DESC
LIMIT 1