Question

I need help with a raw SQL query which gets a value based on another value.

I have the following raw SQL query.

SELECT pmPropDef.id, pmPropDef.name, pmPropDef.units, pmPropShort.str, pmPropLong.str   
 FROM pmProp INNER JOIN pmPropDef ON pmProp.propid=pmPropDef.id AND pmPropDef.name = 'Area' 
 LEFT JOIN pmPropShort ON sid=pmProp.value 
 LEFT JOIN pmPropLong ON lid=-pmProp.value 
 WHERE pmProp.ownertype='variant' AND pmPropDef.id = pmProp.propid;

And this results in the following:

+----+------+-------+------+------+
| id | name | units | str  | str  |
+----+------+-------+------+------+
| 14 | Area | mm2   | 1.1  | NULL |
+----+------+-------+------+------+

The problem that I am getting both pmPropShort.str and pmPropLong.str and I should be betting one or the the other. What I really want is a single str value? How do I re-write this query to meet my needs?

Answer 1

You can use COALESCE which returns the first non-NULL argument. eg.

COALESCE(pmPropShort.str, pmPropLong.str)