CREATE DATABASE goods;

USE goods;
CREATE TABLE `user`(
	userid int primary key auto_increment,
	username varchar(30),
	usersex bit 
);

CREATE TABLE book(
	bookid int primary key auto_increment,
	bookname varchar(30)
);


insert into `user`(username,usersex)
values('张三',0),('李四',0),('王五',0);

insert into book(bookname)
values('C#'),('JS'),('JAVA');

SELECT LENGTH('ASDFG')
SELECT CHAR_LENGTH('ABCDEF')

SELECT REPLACE('ASDFG','G','P')
SELECT INSERT('123456789',5,2,'AB')

SELECT LEFT('123456789',2)
SELECT RIGHT('123456789',5)
SELECT SUBSTRING('123456789',2,3)

SELECT CONCAT('2号','巨帅')

SELECT LOWER('ASDFG')
SELECT UPPER('asdfg')

SELECT REVERSE('123456')

SELECT TRIM('    ASD     ')
SELECT LTRIM('    SAD          ')
SELECT RTRIM('       ASD          ')

SELECT NOW()

SELECT *,IF(usersex=0,'男','女') from `user`

SELECT *,
(
CASE usersex
	WHEN 0 THEN
		'男'
		WHEN 1 THEN
		'女'
	ELSE
		'错误'
END 
)
from user;