mysql 开发基础系列7 流程函数与其它函数

-- 创建表来介绍
CREATE TABLE salary (userid INT,salary DECIMAL(9,2));
INSERT INTO salary VALUES(1,1000),(2,2000), (3,3000),(4,4000),(5,5000), (1,NULL);
SELECT * FROM salary

SELECT IF(salary>2000 ,‘high‘,‘low‘) FROM salary

SELECT IFNULL(salary,0) FROM salary;

SELECT CASE 
WHEN salary<=2000 THEN ‘low‘ 
WHEN salary>=2001 AND salary<=4000 THEN‘middle‘ 
ELSE ‘high‘  END 
FROM salary;

SELECT 
DATABASE() AS ‘数据库名‘,
VERSION() AS ‘数据库版本‘,
USER() AS ‘当前用户名‘,
INET_ATON(‘192.168.1.1‘)AS ‘IP字节‘,
INET_NTOA(3232235777) AS ‘ip字节转IP‘

SELECT PASSWORD(‘123456‘)

SELECT MD5(‘123456‘);