Question

Hi I am running query on two files File1 and File 2 Having fields a,b,c and d,e,f respectively .A and D & B and E are of same type and are keys in the files. So i am running a query to find out all those records of File1 which are not present in File2. I am running the join on the basis to fields a,b and d,e.But some how its not working :

select * from file1 where a,b not in ((select a,b from file1 x,file2 y where y.a=x.d
 and y.b=x.e) z)

It says not in clause not correct then i tried:

select * from file1 where not exists (select a,b from file1 x,file2 y where y.a=x.d
     and y.b=x.e)  

It is also not working !!! Please suggest !I am on DB2 AS400

Answer 1

SELECT *
    FROM file1 f1
    WHERE NOT EXISTS(SELECT NULL
                         FROM file2 f2
                         WHERE f1.a = f2.d
                             AND f1.b = f2.e)

You could also do this with a LEFT JOIN:

SELECT f1.*
    FROM file1 f1
        LEFT JOIN file2 f2
            ON f1.a = f2.d
                AND f1.b = f2.e
    WHERE f2.d IS NULL