第一步：创建一个索引管理表，其中包含，索引名称、最小值、最大值、当前值、增量，并设置主键为索引名称。
CREATE TABLE TB_SEQUENCE ( SEQ_NAME VARCHAR(50) NOT NULL, MINVALUE INT NOT NULL , MAX_VAL DECIMAL(31) NOT NULL, CURRENT_VAL DECIMAL(31) NOT NULL, INCREMENT_VAL INT DEFAULT ‘1‘ NOT NULL, PRIMARY KEY (SEQ_NAME) )
第二步：给索引管理表中插入要实现的一条索引管理数据
INSERT INTO TB_SEQUENCE (SEQ_NAME, MINVALUE, MAX_VAL, CURRENT_VAL, INCREMENT_VAL) values (‘SEQ_NUM‘, 1, 9999999999999999999999999999999, 1, 1);
第三步：创建一个获取下一条数据的函数
DELIMITER $$ create function _nextval(name varchar(50)) returns DECIMAL(31) begin declare _cur DECIMAL(31); declare _maxvalue DECIMAL(31); declare _increment int; declare _nextVal DECIMAL(31); set _cur = (select CURRENT_VAL from TB_SEQUENCE where SEQ_NAME = name); set _increment = (select INCREMENT_VAL from TB_SEQUENCE where SEQ_NAME = name); set _maxvalue = (select MAX_VAL from TB_SEQUENCE where SEQ_NAME = name); set _nextVal = _cur + _increment; update TB_SEQUENCE set CURRENT_VAL = _nextVal where SEQ_NAME = name ; if(_nextVal >= _maxvalue) then update TB_SEQUENCE set CURRENT_VAL = 1 where SEQ_NAME = name ; end if; return _nextVal; end; $$ DELIMITER ;
好了~
测试一下：
select _nextval(‘SEQ_NUM‘) from dual;
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