SQL触发器还是其他？

Question

How can I use trigger to update my table that have status column that is now set on unknown . How can I change this to "open" or "close" depending on the "time_spent" and "time_available" in the table? The status should change automatically when "time_spent" = "time_available".

Answer 1

You don't need a trigger. In fact, you don't even need to store this column. An easier approach would be to calculate it on the fly when you query the table:

SELECT *, CASE time_spent WHEN time_available THEN 'close' ELSE 'open' END
FROM   my_table