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MySQL Demo 01

1. 下面的语句是否可以执行成功

SELECT last_name , job_id , salary AS sal
FROM employees; 

2.下面的语句是否可以执行成功

SELECT  *  FROM employees; 

3.找出下面语句中的错误

SELECT employee_id , last_name,
salary * 12 AS "ANNUAL  SALARY"
FROM employees;

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;

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SELECT
    CONCAT(`first_name`,',',`last_name`,',',`job_id`,',',IFNULL(commission_pct,0)) AS out_put
FROM
    employees;