存在的SQL子查询

Question

I have a scenario that can be described with 3 tables; member, role and memberrole. Memberrole is the intersection of the the other two and I want to fully populate it with an outer join (from member and role). That is the easy part.

Now I want to be able to update the intersection for a new member or new role.

What I want to accomplish looks like this (but is incorrect syntax):

insert into memberrole (memberid,roleid)  
    select member.memberid, role.roleid 
    from member, role 
    where member.memberid, roleid not exists (select memberid, roleid 
                                              from memberrole)

...any suggestions? Thanks

Answer 1

INSERT into memberrole (memberid,roleid)
SELECT m.memberid, r.roleid
FROM member m
JOIN zrole r -- carthesian product MINUS the inner product
        ON NOT EXISTS (select *
        FROM memberrole mr
        WHERE mr.memberid = m.memberid
        AND mr.roleid = r.roleid
    );

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Note: role is a reserved word. I replaced it by zrole .