SQLD(SQL 개발자) 기출 · 서브쿼리

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1. 1.SELECT NAME
   FROM CUSTOMER C
   WHERE C.CUST_ID NOT IN (SELECT CUST_ID FROM CONTRACT);
2. 2.SELECT NAME
   FROM CUSTOMER C
   WHERE EXISTS (SELECT 1 FROM CONTRACT WHERE C.CUST_ID = CUST_ID);
3. 3.SELECT NAME
   FROM CUSTOMER C
   WHERE NOT EXISTS (
   SELECT 1
   FROM CONTRACT CT
   WHERE C.CUST_ID = CT.CUST_ID);
4. 4.SELECT NAME
   FROM CONTRACT
   WHERE CUST_ID IS NULL;