已知Mysql数据库中提供了三个测试数据库表名称分别为deptemp和salgrade。使用SQL语言完成以下操作1试用SQL语言完成下列查询单表查询每题2分共20分 a查询20号部门的所有员工信息： b查询奖金COMM高于工资SAL的员工信息： c查询奖金高于工资的20的员工信息 d查询10号部门中工种为MANAGER和20号部门中工种为CLERK的员工的信息 e查询所有工种

a) SELECT * FROM emp WHERE deptno = 20; b) SELECT * FROM emp WHERE comm > sal; c) SELECT * FROM emp WHERE comm > sal * 0.2; d) SELECT * FROM emp WHERE (deptno = 10 AND job = 'MANAGER') OR (deptno = 20 AND job = 'CLERK'); e) SELECT * FROM emp WHERE job NOT IN ('MANAGER', 'CLERK') AND sal >= 2000; f) SELECT * FROM emp WHERE comm IS NULL OR comm < 100; g) SELECT * FROM emp WHERE TIMESTAMPDIFF(YEAR, hiredate, CURDATE()) >= 10; h) SELECT CONCAT(UPPER(LEFT(ename, 1)), SUBSTRING(ename, 2)) AS ename FROM emp; i) SELECT * FROM emp WHERE MONTH(hiredate) = 2; j) SELECT ename, YEAR(hiredate) AS hire_year, MONTH(hiredate) AS hire_month FROM emp ORDER BY MONTH(hiredate), YEAR(hiredate)