SELECT A.* FROM TABLE_A A WHERE exists (SELECT B.EMPLID from TABLE_B B where A.EMPLID = B.EMPLID and B.UNIT = 'ABC123')
Is an Export script possible?
SELECT A.* FROM TABLE_A A INNER JOIN TABLE_B B ON B.EMPLID = A.EMPLID AND B.UNIT = 'ABC123'
The only problem you will have is if the relationship between TABLE_A and TABLE_B is one-to-many. Since you are using the dreaded, evil "select star"—presumably you did this only for convenience in posing the question, and would not do it in real life—you will find it difficult to use GROUP BY, because the GROUP BY would have to include every column being selected.
But there's an easier way. Push the GROUP BY down into a derived table subquery, so that TABLE_A joins to only one row derived from TABLE_B:
SELECT A.* FROM TABLE_A A INNER JOIN ( SELECT EMPLID FROM TABLE_B WHERE UNIT = 'ABC123' GROUP BY EMPLID ) B ON B.EMPLID = A.EMPLID
This eliminates the one-to-many problem in the outer query.
This was first published in January 2008