Question

i have two tables, tasks and actions. actions has two columns, created_at and updated_at. tasks has a column started_at

how can i do something like

SELECT MAX( UNIX_TIMESTAMP( tasks.started_at ) ) AS started_at, action . * 
FROM tasks, action
WHERE UNIX_TIMESTAMP( action.created_at ) > started_at
OR UNIX_TIMESTAMP( action.updated_at ) > started_at

trying to select all actions that have a greater created_at or updated_at than the MAX(tasks.started_at)

Answer 1

SELECT * FROM actions 
WHERE created_at>(SELECT MAX(started_at) FROM tasks) OR
      updated_at>(SELECT MAX(started_at) FROM tasks)

Don’t worry about performance, by default MySQL should cache SELECT MAX(started_at) FROM tasks value. If you have other configuration add SQL_CACHE to main query: SELECT SQL_CACHE * FROM...