1.下面的语句是否可以执行成功
SELECT last_name , job_id , salary AS sal
FROM employees;
(是)
2.下面的语句是否可以执行成功
SELECT * FROM employees;
(是)
3.找出下面语句中的错误
SELECT employee_id , last_name,
salary * 12 ”ANNUAL SALARY“
FROM employees;
（标点符号需要是英文格式下的）
4.显示表departments的结构，并查询其中的全部数据
DESC departments; SELECT * FROM `departments`;
5.显示出表employees中的全部job_id（不能重复）
SELECT DISTINCT job_id FROM employees;
6.显示出表employees的全部列，各个列之间用逗号连接，列头显示成OUT_PUT
SELECT IFNULL(commission_pct,0) AS 奖金率, commission_pct FROM employees; #------------------------------------------- SELECT CONCAT(`first_name`,',',`last_name`,',',`job_id`,',',IFNULL(commission_pct,0)) AS out_put FROM employees;
