not exist, not in, left join 的写法，不在。。。之内
SELECT T2.DEPTNO FROM DEPT2 T2 WHERE NOT EXISTS (SELECT 1 FROM DEPT WHERE DEPT.DEPTNO = T2.DEPTNO) SELECT T2.DEPTNOFROM DEPT2 T2 WHERE T2.DEPTNO NOT IN (SELECT T1.DEPTNO FROM DEPT T1); SELECT * FROM (SELECT T1.DEPTNO T12, T2.DEPTNO T22 FROM DEPT2 T2 LEFT JOIN DEPT T1 ON T1.DEPTNO = T2.DEPTNO) WHERE T12 IS NULL
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