本文主要内容：
显示表中多有的索引show all index
添加索引ADD INDEX， 添加唯一索引add unique index
多列联合添加索引,primary key
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.
