mysql实现自增序列的示例代码

(编辑：jimmy 日期: 2024/9/21 浏览：2)

1.创建sequence表

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;

2.创建–取当前值的函数

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 ;

3.创建–取下一个值的函数

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 ;

4.创建–更新当前值的函数

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 ;

5.测试添加实例执行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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