How to use not exists in a sql query with w3schools? -

i have issue not exists sql query @ w3schools

i want select customers work shipperid = 1 not shipperid = 3. tried following:

select o1.customerid, o1.shipperid orders o1 o1.shipperid=1 , not exists (select o2.customerid orders o2 o1.orderid=o2.orderid , o2.shipperid=3) order customerid ; 

the above query gives customers work shipperid = 1 , not exclude customers work shipperid = 3. not correct query. (i need speifically use not exists)

---

ps: know in solution:

select customerid, shipperid orders shipperid=1 , customerid not in ( select customerid orders shipperid=3 ) order customerid; 

why not not exists solution work?

i'm problem lies in way you're joining correlated subquery, on orderid = orderid. i'm not familiar dataset, seems surprising same order have different shippers, , adds condition not found in 'correct' answer. should work:

select o1.customerid       ,o1.shipperid orders o1 o1.shipperid = 1  , not exists (     select o2.orderid      orders o2     o1.customerid = o2.customerid     , o2.shipperid = 3) order customerid ;