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  • MySQL实现自增序列

    参考:https://blog.csdn.net/weixin_42383575/article/details/103023379

    新建序列

    ### 新建序列表
    drop table if exists sequence;
    create table sequence(
    seq_name VARCHAR(50)  NOT NULL COMMENT '序列名称',
    current_val INT             NOT NULL COMMENT '当前值',    
    increment_val INT         NOT NULL     DEFAULT 1 COMMENT '跨度',
    PRIMARY KEY(seq_name)
    );
    
    ### 新增一个序列
    INSERT INTO sequence VALUES('seq_test_1', 0, 1);
    INSERT INTO sequence VALUES('seq_test_2', 0, 2);
    
    ### 创建函数用于获取当前序列值
    CREATE FUNCTION currval(v_seq_name VARCHAR(50))
        RETURNS INTEGER
    BEGIN
        DECLARE val INTEGER;
        set val = 0;
        SELECT current_val into val from sequence where seq_name=v_seq_name;
        return val;
    END;
    
    ### 查询当前的值
    SELECT currval('seq_test_1');
    
    ### 创建函数用户获取下一个值
    CREATE FUNCTION nextval(v_seq_name VARCHAR(50))
        RETURNS INTEGER
    BEGIN
        UPDATE sequence SET current_val = current_val + increment_val where seq_name=v_seq_name;
        return currval(v_seq_name);
    END;
    
    ### 查询下一个值
    SELECT nextval('seq_test_1');

    创建表测试

    ### 新建测试表
    DROP TABLE IF EXISTS `sequence_test`;
    CREATE TABLE `sequence_test` (
      `name` varchar(255) NOT NULL,
      `value` double(255,2) DEFAULT NULL,
      `num1` int(11) DEFAULT NULL,
      `num2` int(11) DEFAULT NULL,
      PRIMARY KEY (`name`)
    );
    
    ### 新建触发器 插入记录前给自增字段赋值
    DROP TRIGGER IF EXISTS `TRI_TEST_SEQ`;
    CREATE TRIGGER `TRI_TEST_SEQ` BEFORE INSERT ON `sequence_test` FOR EACH ROW BEGIN
    SET NEW.num1 = nextval('seq_test_1');
    SET NEW.num2 = nextval('seq_test_2');
    END;
    
    
    ### 测试效果
    INSERT INTO sequence_test(name, value) VALUES('1', 111);
    INSERT INTO sequence_test(name, value) VALUES('2', 111);
    INSERT INTO sequence_test(name, value) VALUES('3', 111);
    INSERT INTO sequence_test(name, value) VALUES('4', 111);
    
    ### 结果展示
    SELECT * FROM sequence_test;
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  • 原文地址:https://www.cnblogs.com/eason-d/p/15766503.html
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