mysql索引index相关命令的详细介绍

本文主要内容：

1. 显示表中多有的索引show all index

2. 添加索引ADD INDEX， 添加唯一索引add unique index

3. 多列联合添加索引,primary key

4. 关键词index vs key

show all index

show index from tb_name 例如：

show index from springdemo.blog;

添加索引ADD INDEX， 添加唯一索引add unique index

ALTER TABLE `table` ADD INDEX `product_id` (`product_id`)

# 创建唯一索引alter table tb_name  add unique index  `unique_idsrc_caffeversion` (`id_src`, `caffe_version`)

多列联合索引，添加主键

#多列索引ALTER TABLE `table` ADD INDEX `index_name` (`col1`,`col2`)

# add primary key 添加主键ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` )

关键词index vs key

在创建表的时候，这两个关键词没什么区别，相当于同义词

What are differences between Index v.s. Key in MySQL

CREATE TABLE tasks ( 
task_id INT UNSIGNED NOT NULL AUTO_INCREMENT, 
INDEX parent (parent_id), 
....# However I found a code using KEY instead of INDEX as following....KEY order_date (order_date) 
...

There’s no difference. They are synonyms.This was implemented for 
 compatibility with other database systems.

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