如何在 MySQL 中创建两个自增列? [英] How to create two auto increment columns in MySQL?

问题描述

CREATE TRIGGER test1 AFTER INSERT ON `course_metadata_31`
FOR EACH ROW BEGIN
    UPDATE `course_metadata_31`
    SET `articleID` = `articleID` + 1
END;

我正在使用这种方法.当我将在 course_metadata_31 中插入新条目时，它也应该增加 articleID.因为我想要 articleID 作为另一个自增列.

I am using this approach. When I will insert new entry in course_metadata_31 it should increment articleID too. Because I want articleID as another auto increment column.

我该怎么办?

推荐答案

不知道为什么你需要两列自动递增的值，没有意义...但如果你坚持 -
你可以在 UDF 中完成或 SP 这样你就有多个列自动递增一个值.

No idea why you need two columns auto incrementing values, there is no point... but if you insist -
You can accomplish it in a UDF or SP this way you have multiple columns auto incrementing a value.

示例 1:存储过程 (SP)


表格

CREATE TABLE tests (
    test_id INT(10) NOT NULL PRIMARY KEY AUTO_INCREMENT,
    test_num INT(10) NULL,
    test_name VARCHAR(10) NOT NULL
);

存储过程

DELIMITER $$
CREATE PROCEDURE autoInc (name VARCHAR(10))
    BEGIN
        DECLARE getCount INT(10);

        SET getCount = (
            SELECT COUNT(test_num)
            FROM tests) + 1;

        INSERT INTO tests (test_num, test_name)
            VALUES (getCount, name);
    END$$
DELIMITER ;

致电 SP

CALL autoInc('one');
CALL autoInc('two');
CALL autoInc('three');

查表

SELECT * FROM tests;

+---------+----------+-----------+
| test_id | test_num | test_name |
+---------+----------+-----------+
|       1 |       1  | one       |
|       2 |       2  | two       |
|       3 |       3  | three     |
+---------+----------+-----------+

<小时>
示例 2:用户定义的函数 (UDF)


表格

CREATE TABLE tests (
    test_id INT(10) NOT NULL PRIMARY KEY AUTO_INCREMENT,
    test_num INT(10) NULL,
    test_name VARCHAR(10) NOT NULL
);

用户自定义函数

DELIMITER $$
CREATE FUNCTION autoInc ()
    RETURNS INT(10)
    BEGIN
        DECLARE getCount INT(10);

        SET getCount = (
            SELECT COUNT(test_num)
            FROM tests) + 1;

        RETURN getCount;
    END$$
DELIMITER ;

使用 UDF 插入

INSERT INTO tests (test_num, test_name) VALUES (autoInc(), 'one');
INSERT INTO tests (test_num, test_name) VALUES (autoInc(), 'two');
INSERT INTO tests (test_num, test_name) VALUES (autoInc(), 'three');

查表

SELECT * FROM tests;

+---------+----------+-----------+
| test_id | test_num | test_name |
+---------+----------+-----------+
|       1 |       1  | one       |
|       2 |       2  | two       |
|       3 |       3  | three     |
+---------+----------+-----------+

这些已经过测试和验证.我个人会使用这个功能，它更灵活.

These have been tested and verified. I'd personally use the function, it's more flexible.

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