PhpMyAdmin

Question

我在使用 PhpMyAdmin 时遇到了困难。我的 table 是：

material(id_item, id_collection,...)
primarey_key(id_item, id_collection).

我想制作一个函数来防止无环图数据库中的循环。所以我想强制 id_collection > id_item 新 id_collection.

我的功能是（我在SQL选项卡中设置了//）：

    //

CREATE or REPLACE function collections_prevent_cycle()
 BEGIN
    DECLARE max_of_both SMALLINT;
    SET max_of_both := (MAX(GREATEST(id_item, id_collection)) FROM material);

    IF NOT EXISTS(SELECT id_collection FROM material where id_collection = NEW.id_collection) THEN
        IF (NEW.id_item >= max_of_both) THEN SIGNAL SQLSTATE '45000'
            SET MESSAGE_TEXT = 'You may not insert items that doesnt exist';

        ELSEIF(NEW.id_collection <> max_of_both + 1) THEN SIGNAL'45000'
            SET MESSAGE_TEXT = 'You may not insert non stable id_collection';
        END IF;
    END IF;
    RETURN 0;
 END;

//

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'function collections_prevent_cycle() RETURN integer BEGIN DECLARE max_of_b' at line 1

我正在弄乱声明但无法摆脱 - 任何人都可以帮助我吗？

修复了我的第一个定界符 pbm：

Delimiter in PhpMyadmin

Answer 1

终于找到了错误的解决方法。

第一个：

It seems u can't use NEW & OLD keywords in function on MYSQL. So i made a Trigger instead.

Switched to Adminer instead of PHPmyAdmin to use DELIMITER I notice DELIMITER*(space)$$* means (space)$$ and not only $$

SET := didn't work so I use basic SELECT ... INTO... FROM

CREATE or Replace doesn't existe - u have to separate operations.

这是我编译但无法运行的代码。

DELIMITER $$
DROP trigger IF EXISTS collections_prevent_cycle $$
CREATE trigger collections_prevent_cycle 
BEFORE insert ON material FOR EACH ROW BEGIN

    DECLARE max_of_id_item SMALLINT;
    DECLARE max_of_both SMALLINT;

    SELECT MAX(GREATEST(id_item, id_collection))     
    INTO max_of_both    
    FROM material;

    SELECT MAX(id_item)
    INTO max_of_id_item
    FROM material;

    IF ((SELECT id_collection 
          FROM material 
          WHERE id_collection = NEW.id_collection) = NULL) THEN
            IF (NEW.id_item > max_of_id_item) THEN             
                SIGNAL SQLSTATE '45000'
                SET MESSAGE_TEXT = 'You may not insert items that doesnt exist';

            ELSEIF (NEW.id_collection <> max_of_both + 1) THEN             
                SIGNAL SQLSTATE '45000'            
                SET MESSAGE_TEXT = 'You may not insert non stable id_collection';
            END IF;
    END IF;
END $$
DELIMITER ;

我的目标是以这种方式强制插入：

如果添加新的 collection id - 它必须是（collection 和项目的最大 id）+ 1
如果添加新的 collection id - 它必须包含现有项目 (id_item < max(id_item))

如果有人知道为什么触发器不触发 - 我没油了:'(.

编辑：我测试了两个子嵌套 IF (IF & ELSEIF) 它们单独工作。

因此这是第一个失败的 IF。

我想 = NULL 是不够的，但无法在查询可能结果的文档中找到答案。

我这样挖 - 如果有人有一个漂亮的解决方案，我会采纳。河童

编辑 2：有效！

(SELECT count(*) 
          FROM material 
          WHERE id_collection = NEW.id_collection) = 0)

已替换通过

(SELECT count(*) 
          FROM material 
          WHERE id_collection = NEW.id_collection) = 0)

所以当它为空时查询 returns 0（而不是这个明显的空资源）。

我赢了！

PhpMyAdmin - 错误 1064 - 在函数中设置变量

PhpMyAdmin - err 1064 - set variable in function

mysql-error-1064