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MySQL-07

2022-06-26 05:58:00 【Mr.Rop】

7、 Indexes

MySQL The official definition of index is ： Indexes （index） Help MySQL Data structure for efficient data acquisition . Extract the sentence trunk , We can get the essence of index ： An index is a data structure .

7.1、 Classification of indexes

In a table , The primary key index can only have one , There can be more than one unique index

primary key （PRIMARY KEY）
- Unique identification , Do not repeat , There can only be one column as the primary key
unique index （UNIQUE KEY）
- Avoid duplicate columns , The unique index can be repeated , Multiple columns can identify bits unique index
General index （KEY/INDEX）
- default ,index,key Keyword to set
Full-text index （FULLText）
- Under a specific database engine ,MyISAM
- Quickly locate data

Basic grammar

--  Use of index 
-- 1、 Add indexes to fields when creating tables 
-- 2、 After creation , Add index 

--  Show all information 
SHOW INDEX FROM student

--  Add an index 
ALTER TABLE school.student ADD FULLTEXT INDEX `StudentName` (`StudentName`);

--  analysis sql Execution status 
EXPLAIN SELECT * FROM student; --  General index , Non full text index 

EXPLAIN SELECT * FROM student WHERE MATCH(StudentName) AGAINST(' Zhang ')

7.2、 Test index

CREATE TABLE `app_user` (
  `id` BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(50) DEFAULT '' COMMENT ' The user nickname ',
  `eamil` VARCHAR(50) NOT NULL COMMENT ' User mailbox ',
  `phone` VARCHAR(20) DEFAULT '' COMMENT ' cell-phone number ',
  `gender` TINYINT(4) UNSIGNED DEFAULT '0' COMMENT ' Gender （0： male ;1： Woman ）',
  `password` VARCHAR(100) NOT NULL DEFAULT '' COMMENT ' password ',
  `age` TINYINT(4) DEFAULT NULL COMMENT ' Age ',
  `create_time` DATETIME DEFAULT CURRENT_TIMESTAMP,
  `update_time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8

--  Insert 100 Ten thousand data 
DELIMITER $$ --  Before you write a function, you have to write , sign 
CREATE FUNCTION mock_data()
RETURNS INT
BEGIN
  DECLARE num INT DEFAULT 1000000;
  DECLARE i INT DEFAULT 0;
  
  WHILE i<num   DO
	--  Insert statement 
	INSERT INTO app_user(`name`,`eamil`,`phone`,`gender`,`password`,`age`)
        VALUES(CONCAT(' user ',i),'[email protected]'
        ,CONCAT('18',FLOOR(RAND()*(999999999-1000000000)+100000000))
        ,FLOOR(RAND()*2),UUID(),FLOOR(RAND()*100));
	SET i =i+1;
  END WHILE;
  RETURN i;
END;
SELECT mock_data();

--  test 

SELECT * FROM app_user WHERE `name` =' user 9999';
SELECT * FROM app_user WHERE `name` =' user 9999';

EXPLAIN SELECT * FROM app_user WHERE `name` =' user 9999';

SELECT * FROM student;

-- id_ Table name _ Field name 
CREATE INDEX id_app_user_name ON app_user (`name`);
SELECT * FROM app_user WHERE `name` =' user 9999';
EXPLAIN SELECT * FROM app_user WHERE `name` =' user 9999';