Question

I have a query say,

select col1,col2 from table1;

which return 2 columns of multiple rows. I want to use these two values in where condition of another query. Something like

select col3,col4 from table2 where col5=col1 and col6=col2;

where col1 and col2 are the resultant values of the first query.

Currently I have used inner query something like

select col3,col4 from table2 
where col5 in (select col1 from table1) 
  and col6 in (select col2 from table1);

But I dont want to use inner query like the one shown above as it slows down bring results.

Please suggest.

Answer 1

JOIN them instead of using IN‘s like so:

SELECT t2.col3, t2.col4 
FROM table2 t2
INNER JOIN
(
   SELECT col1, col2 
   FROM table1
) t1 ON t2.col5 = t1.col1 AND t2.col6 = t1.col2

Note that, you didn’t need to select specific columns in the second table. You can JOIN the second table table1 directly like so:

SELECT t2.col3, t2.col4 
FROM table2 t2
INNER JOIN table1 t1 ON  t2.col5 = t1.col1 
                     AND t2.col6 = t1.col2