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.
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;
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 ;
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 ;
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 ;
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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