Oracle SQL：将所有用户放在一个表中，而不是另一个表中，并加入第三个表

Question

I am wondering how to use oracle sql to get all the rows that are in one table but not another. The issue I am having is that the two tables don't have a field in common so I need to join to a third master table.

This is what I've tried which doesn't produce any errors but also produces 0 records which isn't possible but clearly I've done something wrong.

 SELECT a.USER_ID, c.AD_ID, c.CREATED_DATE_ FROM $A$ a, $C$ c, $B$ b 
 WHERE (b.USER_ID IS NULL AND a.CUSTOMER_ID = c.CUSTOMER_ID) 

I have three tables:

Table A has fields CUSTOMER_ID & USER_ID

Table B has field USER_ID

Table C has field CUSTOMER_ID

I need all the users that are in table C but not table B. They are all in Table A because that is the master list of users.

Any insight would be greatly appreciated.

Answer 1

SELECT
  *
FROM
  table_a
WHERE
  NOT EXISTS (SELECT * FROM table_b WHERE table_b.user_id     = table_a.user_id    )
  AND EXISTS (SELECT * FROM table_c WHERE table_c.customer_id = table_a.customer_id)

Answer 2

My solution:

select * from TableC tc
join TableA ta on tc.CUSTOMER_ID=ta.CUSTOMER_ID
left join TableB tb on tb.USER_ID=ta.USER_ID
where ta.USER_ID is null

Answer 3

I think you want:

select a.USER_ID, c.AD_ID, c.CREATED_DATE_
from a join
     c
     on a.customer_id = c.customer_id
where not exists (select 1 from b where b.user_id = a.user_id);