Introduction to mysql index types

Introduction to index types:

Primary key index

primary key() requires that the keyword cannot be repeated or null ,When adding primary key constraints and defining the primary key index, you cannot name

unique index

##unique index() requires that keywords cannot be repeated, and also add unique constraints

Normal index

index() has no requirement for keywords

Full text index

fulltext key() keyword The source is not the data of all fields, but the special keywords extracted from the fields: it can be a certain field or multiple fields, and multiple fields are called composite indexes.

Example:

建表：
creat table student(
    stu_id int unsigned not null auto_increment,
    name varchar(32) not null default '',
    phone char(11) not null default '',
    stu_code varchar(32) not null default '',
    stu_desc text,
    primary key ('stu_id'),     //主键索引
    unique index 'stu_code' ('stu_code'), //唯一索引
    index 'name_phone' ('name','phone'),  //普通索引，复合索引
    fulltext index 'stu_desc' ('stu_desc'), //全文索引) engine=myisam charset=utf8;

更新：
alert table student    add primary key ('stu_id'),     //主键索引
    add unique index 'stu_code' ('stu_code'), //唯一索引
    add index 'name_phone' ('name','phone'),  //普通索引，复合索引
    add fulltext index 'stu_desc' ('stu_desc'); //全文索引删除：
alert table sutdent
    drop primary key,
    drop index 'stu_code',
    drop index 'name_phone',
    drop index 'stu_desc';

Recommended tutorial:
mysql tutorial

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