SQL优化：查询销售部员工姓名

{"title":"分析sql","description":"列出在部门"sales"（销售部）工作的员工的姓名，假定不知道销售部的部门编号\nselect ename from emp where deptno=(\n select deptno from emp where job='CLERK'\n);\nSubquery returns more than 1 row\n给出优化的sql内容：优化的SQL如下：\n\nSELECT ename \nFROM emp \nWHERE deptno IN (\n SELECT deptno \n FROM emp \n WHERE job='CLERK'\n) AND job='SALESMAN';"}