Question

I have two tables, one that stores serial number uut_build, and another for measurements that belong to the serial numbers measure_list, I’m trying to get the count of records in measure_list that belongs to a unique serial number.
Query #1

select id, uut_sn from uut_build where uut_sn like 'A%';

Query #2

select count(*) from measure_list as m WHERE m.uut_id = [result from query #1]

Is it possible to do this with just one query statement?

Thanks in advance!

Answer 1

Use:

   SELECT ub.uut_sn,
          COALESCE(COUNT(ml.*), 0) AS cnt
     FROM UUT_BUILD ub
LEFT JOIN MEASURE_LIST ml ON ml.uut_id = ub.uut_sn
    WHERE ub.uut_sn LIKE 'A%'
 GROUP BY ub.uut_sn

It’s a little unclear what columns link the two tables…

This will return all serial numbers – if they don’t have a record in MEASURE_LIST, the cnt value will be zero. If you only want a list of records that have records in MEASURE_LIST, remove “LEFT” from the query I provided.