Correlated mysql subqueries

Question

HI i want to get the value of the variable from the main query inside the sub query

SELECT t1.,sq.,count(distinct(t4.col1)) as count, FROM t1 LEFT OUTER JOIN( SELECT t2.col1, t2.col2, t2.col3 FROM t2 WHERE t2.col1=t1.col1
ORDER BY t2.col2 DESC, t2.col1 DESC ) as sq ON sq.col1=t1.col1
LEFT OUTER JOIN t3 ON t3.col1=t1.col4 LEFT OUTER JOIN t4 ON t4.col1=t1.col4 WHERE t3.col2=x GROUP BY t1.col3 LIMIT 15

How do i get the value of the variable t1.col1 inside the subquery sq when I am joining it on the same column??

Answer 1

You can't but following should return equivalent results as the query you've posted.

SELECT  t1.col3            
FROM    t1 
        left outer join ( 
          select  t2.col1
                  ,t2.col2
                  ,t2.col3 
                  ,t2.col4
          FROM    t2 
        ) as sq on sq.col1 = t1.col1 
                   AND sq.col4 = t1.col1
where   t1.col2 = x 
group by 
        t1.col3 
limit 15

Note: the original query you've posted contains a few syntax errors.

• select * with group by
• order by in a subselect
• using the outer select in the subselect (your question)