Question

我正在研究删除邻接表模型中存储的树的子树的方法。我设置了此代码，该代码使用ON DELETE CASCADE删除了完整的树。当我将 max _ 设置为值> 14时，MariaDB（Windows）会引发以下错误：

出现错误193'mydb。tree，约束tree_ibfk_1，外键（parentid）参考tree（nodeid）删除级联来自InnoDB

是我的代码还是数据库的限制？

DROP TABLE IF EXISTS tree;
DROP PROCEDURE IF EXISTS prepTree;

CREATE TABLE tree (
    name varchar(255) NOT NULL,
    nodeid INT NOT NULL AUTO_INCREMENT,
    parentid INT NULL,
    PRIMARY KEY(nodeid),
    FOREIGN KEY(parentid) REFERENCES tree(nodeid) ON DELETE CASCADE
) ENGINE=InnoDB;

DELIMITER // ;
CREATE PROCEDURE prepTree()
    BEGIN
        DECLARE i INT;
        DECLARE max_ INT;

        SET max_ = 15; -- >14 won't work

        INSERT INTO tree(name, parentid) VALUES("root", NULL);

        SET i = 1;  
        WHILE i <= max_ DO
            INSERT INTO tree(name, parentid) VALUES("child", i);        
            SET i = i + 1;
        END WHILE;

    END //
DELIMITER ; //

CALL prepTree; 

DELETE FROM tree WHERE name = "root";
SELECT * FROM tree; --table will be empty on success

Answer 1

我知道它同样适用于MariaDB。

15.8.1.6 InnoDB and FOREIGN KEY Constraints

...

参考操作

...


...级联操作的嵌套深度不能超过15级。


...

使用ON DELETE CASCADE删除深度嵌套的子树

1 个答案: