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How to implement auto-increment sequence in mysql

醉折花枝作酒筹
Release: 2021-07-12 17:14:28
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This article will introduce to you how to implement auto-increment sequence in mysql. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

How to implement auto-increment sequence in mysql

1. Create a sequence table

CREATE TABLE `sequence` (
  `name` varchar(50) COLLATE utf8_bin NOT NULL COMMENT '序列的名字',
  `current_value` int(11) NOT NULL COMMENT '序列的当前值',
  `increment` int(11) NOT NULL DEFAULT '1' COMMENT '序列的自增值',
  PRIMARY KEY (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
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2. Create a function that takes the current value

DROP FUNCTION IF EXISTS currval; 
DELIMITER $ 
CREATE FUNCTION currval (seq_name VARCHAR(50)) 
     RETURNS INTEGER
     LANGUAGE SQL 
     DETERMINISTIC 
     CONTAINS SQL 
     SQL SECURITY DEFINER 
     COMMENT ''
BEGIN
     DECLARE value INTEGER; 
     SET value = 0; 
     SELECT current_value INTO value 
          FROM sequence
          WHERE name = seq_name; 
     RETURN value; 
END
$ 
DELIMITER ;
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3. Create a function that takes the next one Value function

DROP FUNCTION IF EXISTS nextval; 
DELIMITER $ 
CREATE FUNCTION nextval (seq_name VARCHAR(50)) 
     RETURNS INTEGER 
     LANGUAGE SQL 
     DETERMINISTIC 
     CONTAINS SQL 
     SQL SECURITY DEFINER 
     COMMENT '' 
BEGIN 
     UPDATE sequence 
          SET current_value = current_value + increment 
          WHERE name = seq_name; 
     RETURN currval(seq_name); 
END 
$ 
DELIMITER ;
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4. Create a function that updates the current value

DROP FUNCTION IF EXISTS setval; 
DELIMITER $ 
CREATE FUNCTION setval (seq_name VARCHAR(50), value INTEGER) 
     RETURNS INTEGER 
     LANGUAGE SQL 
     DETERMINISTIC 
     CONTAINS SQL 
     SQL SECURITY DEFINER 
     COMMENT '' 
BEGIN 
     UPDATE sequence 
          SET current_value = value 
          WHERE name = seq_name; 
     RETURN currval(seq_name); 
END 
$ 
DELIMITER ;
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5. Test to add an instance to execute sql

INSERT INTO sequence VALUES ('testSeq', 0, 1);-- 添加一个sequence名称和初始值,以及自增幅度

SELECT SETVAL('testSeq', 10);-- 设置指定sequence的初始值

SELECT CURRVAL('testSeq');-- 查询指定sequence的当前值

SELECT NEXTVAL('testSeq');-- 查询指定sequence的下一个值
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