select IFNULL(col1, (select col2 from table2 where ...)) from table1
Will it run select for table2 if table1 would have not null value? This is a speed issue question. I have no appropriate database to check.
select IFNULL(col1, (select col2 from table2 where ...)) from table1
Will it run select for table2 if table1 would have not null value? This is a speed issue question. I have no appropriate database to check.