SELECT ename, job, sal, dname
FROM emp, dept
WHERE emp.deptno = dept.deptno
AND NOT EXISTS
( SELECT *
FROM salgrade
WHERE emp.sal BETWEEN losal AND hisal )
恕小弟才疏学浅,我始终弄不明白,该怎么看执行计划 以下的语句是我想看的语句 SELECT ename, job, sal, dname FROM emp, dept WHERE emp.deptno = dept.deptno AND NOT EXISTS ( SELECT * FROM salgrade WHERE emp.sal BETWEEN losal AND hisal ) 我选中后后,右击选择了执行计划,截图如下所示, 我想知道的是 一 cost和cardinality分别代表什么意