SQL：左外部联接中的条件

Question

Election:

EID PID    PlanCode     Coverage
2   49791   DELTA        FAMILY
2   49791   LIGNA        FAMILY
2   49791   BSP          FAMILY
2   49792   BSP          FAMILY
2   49792   LIGNA        FAMILY
2   49792   DELTA        FAMILY
2   49793   LIGNA        FAMILY

relationship Table:

EID     PID
2   49791
2   49792
2   49793

table Desc:

Relationship: Employee has 3 dependents

Election:For each Pid, an employee chooses a particular Plan

Problem:

As Pid:49793 enroll in LigNa plan only, trying to add 2 rows for remaining plan ie delta,BSP row

Can we do it as plan name is not fixed, but we know of dependents in relationship table?

Please suggest..

PS: Its working now using cross Join

Answer 1

If am not wrong you are trying to insert the missing PlanCode for each EID,PID combination. Am not very sure about the link of LEFT JOIN usage with this question unless I missed something

INSERT INTO Election
            (EID,PID,PlanCode,Coverage)
SELECT A.EID,A.PID,B.PlanCode,A.Coverage
FROM   (SELECT DISTINCT EID,PID,Coverage
        FROM   Election) A
       CROSS JOIN (SELECT DISTINCT PlanCode
                   FROM   Election) B
WHERE  NOT EXISTS (SELECT 1
                   FROM   Election C
                   WHERE  A.EID = C.EID
                          AND A.PID = C.PID
                          AND B.PlanCode = C.PlanCode)