Mysql学习笔记（附一）

最新推荐文章于 2025-09-11 20:53:34 发布

转载最新推荐文章于 2025-09-11 20:53:34 发布 · 120 阅读

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原文链接：http://www.cnblogs.com/laohan1221/p/5802458.html

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#数据库

本文详细介绍了MySQL中创建表的基本语法，并展示了如何定义不同的字段类型与约束条件。此外，还介绍了如何创建多列索引，以提高特定查询操作的效率。

关于外键约束关系下修改或者删除表的方法：

http://wenku.baidu.com/link?url=RRaI160kvsdf7ibMLqxN815RvStSyenz_-ig1ONfpRfpfFpqtbGQIL4w3IhAw3XySR7Jfxn4Pncl68bIm3qQ_ZZkpJj_HoBt6tFVLa_IHsu

mysql中key 、primary key 、unique key 与index区别：

http://zccst.iteye.com/blog/1697043

CREATE TABLE products(
	id INT NOT NULL AUTO_INCREMENT,
	cid INT NOT NULL DEFAULT '0',
	name VARCHAR(60) NOT NULL DEFAULT '',
	price DOUBLE(7,2) NOT NULL DEFAULT '0.00',
	num INT NOT NULL DEFAULT '0',
	decn TEXT,
	ptime INT NOT NULL DEFAULT '0',
	PRIMARY KEY(id),
	KEY pname(name,price)
);
解析：KEY pname(name,price)	//括号里面有多个，表示创建多列索引，意思是创建名为pname的关于name和price的索引。

CREATE TABLE cats(
	id INT NOT NULL AUTO_INCREMENT,
	pid INT NOT NULL DEFAULT '0',
	name VARCHAR(60) NOT NULL DEFAULT '',
	desn TEXT,
	PRIMARY KEY(id),
	INDEX name(name,pid)
);

INSERT INTO
cats(pid,name,desn)
values(0,'soft','this is soft'),
(1,'java','this is java'),
(1,'php'),
(1,'c++'),
(2,'j2se'),
(2,'j2ee'),
(2,'j2me'),
(3,'php');

INSERT INTO 
products(cid,name,price,num,desn,ptime)
values(1,'javajava','134.5','10','good','123423'),
(1,'javaone','245.5','24','very good','5345345'),
(2,'javasd','445.5','24','very good','5345245'),
(2,'javsdf','455.5','24','very good','534345'),
(3,'asdf','456.5','24','very good','53445'),
(3,'javasadftwo','415.5','24','very good','54545'),
(4,'javatsdwo','452.5','24','very good','55434'),
(4,'jadfvatwo','415.5','24','very good','534545'),
(4,'jasdfvatwo','145.5','24','very good','534545'),
(4,'javsdfatwo','1245.5','24','very good','534445'),
(5,'javgfdatwo','12245.5','24','very good','535445'),
(5,'javatwo','1245.5','24','very good','55345'),
(5,'javatghwo','1545.5','24','very good','53355'),
(6,'javatfgwo','2845.5','24','very good','534445'),
(6,'javafgtwo','845.5','24','very good','53425'),
(7,'javatghwo','8545.5','24','very good','34345'),
(7,'javatjkwo','5645.5','24','very good','5342345'),
(7,'javatweto','2745.5','24','very good','534545'),
(7,'javatrtwo','8245.5','24','very good','534545'),
(7,'javatwrto','2445.5','24','very good','5345345'),
(8,'javatwweo','1645.5','24','very good','534545'),
(8,'javawetweo','1345.5','24','very good','5342345'),
(8,'javwatwwo','1845.5','24','very good','53456345'),
(8,'javawetwo','1565.5','24','very good','53345'),
(2,'javatwcvo','13745.5','24','very good','5342545'),
(1,'javatdfwo','17345.5','24','very good','534475'),
(1,'javatwco','3445.5','24','very good','534345');

转载于:https://www.cnblogs.com/laohan1221/p/5802458.html