The subquery is returning more than one row, and you are using it in a context where only one row should be returned. Perhaps you need to correlate it with the outer query so only one row will be returned, or may be use an aggregate function such as MAX to return only one row?( SELECT REL.REL_NAME FROM RELEASES JOIN RELEASE_CYCLES RCY_CY ON RCY_CY.RCYC_ID = CY_ASSIGN_RCYC JOIN RELEASES REL ON REL.REL_ID = RCY_CY.RCYC_PARENT_ID WHERE REL.REL_ID = OUTERTABLE.REL_ID ) AS "Test Set Assigned Release",
Or if it indeed should return multiple rows, you need to make it into a virtual table and join with the outer table? .... s.REL_NAME as "Test Set Assigned Release" ... FROM OUTERTABLE o INNER JOIN ( SELECT REL.REL_NAME, REL.SOME_JOIN_COLUMN FROM RELEASES JOIN RELEASE_CYCLES RCY_CY ON RCY_CY.RCYC_ID = CY_ASSIGN_RCYC JOIN RELEASES REL ON REL.REL_ID = RCY_CY.RCYC_PARENT_ID WHERE REL.REL_ID = OUTERTABLE.REL_ID ) AS s on S.SOME_JOIN_COLUMN = OUTERTABLE.SOMEJOINCOLUMN ....