记录建表操作

students数据库

CREATE DATABASE school;
USE `school`;

CREATE TABLE `students`(
	`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,  -- 设置为关键字
	`name` VARCHAR(20) NOT NULL,
	`nickname` VARCHAR(20) NULL,
	`sex` CHAR(1) NULL,
	`in_time` DATETIME NOT NULL
) DEFAULT CHARSET 'UTF8';  -- 确定编码为 UTF8

USE `school`;
-- 插入语句
INSERT INTO `students` VALUES(1, '张三', '三哥', '男', now());

INSERT INTO `students` (`name`, `nickname`, `sex`, `in_time`) VALUES
	('李四', '李哥', '男', now()),
	('铁牛', '铁哥', '男', now()),
	('苍井空', '空姐', '女', now());
    -- 多个数据插入, 用逗号隔开, 注意括号要一一对应


SELECT * FROM `students`;  -- 输出全部内容
SELECT * FROM `students` WHERE `sex` = '男';  -- 输出性别为男的内容
SELECT * FROM `students` WHERE `sex` = '男' ORDER BY `id` DESC;  -- 以id倒叙输出
SELECT * FROM `students` WHERE `sex` = '男' ORDER BY `id`  LIMIT 1, 4;
-- --LIMIT [第一条数据的索引],[本次打印数据的数量]

-- 修改
UPDATE `students` SET `sex`  = '女', `nickname` = '大壮' WHERE `sex` = '男';
-- 修改所有
UPDATE `students` SET `sex` = '女', nickname = '三哥';  
-- 修改性别
UPDATE `students` SET `sex` = '男' WHERE `id` < 4;
UPDATE `students` SET `sex` = '女' WHERE `id` = 4;
-- 删除
DELETE FROM `students` WHERE `sex` = '男';

增加列

alter table 表名 add column 列名 varchar(30);