- 建表与插入数据
- SQL对比
基本数据
- 创建表 CREATE TABLE student ( id int(10) NOT NULL AUTO_INCREMENT, name varchar(25) DEFAULT NULL, age tinyint(2) DEFAULT NULL, live varchar(255) DEFAULT NULL, PRIMARY KEY (id) ) ;
- 批量插入1百万条数据
DROP PROCEDURE IF EXISTS insert_Stu;
DELIMITER $$
CREATE PROCEDURE insert_Stu(IN max_num INT(10))
BEGIN
DECLARE i INT DEFAULT 0;
REPEAT
SET i = i 1;
INSERT INTO student (name, age, live) VALUES (rand_string(3), rand_num(), rand_string(6));
UNTIL i = max_num
END REPEAT;
COMMIT;
END $$
DROP PROCEDURE IF EXISTS rand_string;
DELIMITER $$
CREATE FUNCTION rand_string(n INT) RETURNS VARCHAR(255)
BEGIN
DECLARE chars_str VARCHAR(100) DEFAULT 'abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ';
DECLARE return_str VARCHAR(255) DEFAULT '';
DECLARE i INT DEFAULT 0;
WHILE i < n DO
SET return_str = CONCAT(return_str, SUBSTRING(chars_str, FLOOR(1 RAND() * 52), 1));
SET i = i 1;
END WHILE;
RETURN return_str;
END $$;
DROP PROCEDURE IF EXISTS rand_num;
DELIMITER $$
CREATE FUNCTION rand_num()
RETURNS INT(5)
BEGIN
DECLARE i INT DEFAULT 0;
SET i = FLOOR(100 RAND() * 10);
RETURN i;
END $$
;
call insert_Stu(1000000);SQL对比
- 常规分页 select s.* from student s limit 1000000,10;
- 优化分页 select s.* from student s WHERE s.id >= (SELECT s.id FROM student LIMIT 1000000, 1) LIMIT 10;
- 最优分页 SELECT s.* FROM student s WHERE s.id BETWEEN 1000000 AND 1000010;
- 性能对比图 可以看到三种SQL的耗时 ，为什么会有这么大的差距，这主要是MySQL的limit关键字会导致偏移量的原因
image.png
