Question

I have some problems with an (My)SQL query. In my DB I have two tables. One is called kfz_typen, the other kfz_temp2. I need to get all entries of the kfz_temp2 table, which ktyp (just an integer field) is not in the kfz_typen table.

 SELECT * FROM kfz_temp2
 WHERE kfz_temp2.KType NOT IN (SELECT DISTINCT kfz_typen.ktyp FROM kfz_typen)

In my opinion this query above should exactly do, what I want. But it doesn’t! I just get an empty result back from my MySQL Server.

Without the “NOT” in the Query, I get the entries that are in both tables, so the matching does work.

So what’s wrong with the Query above?

Answer 1

Would this work?

SELECT t2.* FROM kfz_temp2 t2
 LEFT JOIN kfz_typen tn ON t2.KType = tn.ktyp
WHERE tn.ktyp IS NULL

You may need to group the result.

I’m unsure why the first query doesn’t work, but I believe this does the same thing.