Question

我想创建一个只在满足条件时插入表的触发器。我尝试过使用IF / BEGIN / END和WHERE的各种组合，但Django每次都会返回一个SQL语法错误。

这里，type_user_id指的是触发类似的人，user_id指的是接收通知的人。它应该只在他们不是同一个人时触发。

a = [1,2]
[a] = [[1,2]]

和

operations = [

    migrations.RunSQL(
        "DROP TRIGGER like_notification",
        """
        CREATE TRIGGER like_notification AFTER INSERT ON user_likes_article
        FOR EACH ROW
        IF (select user_id from channel WHERE channel_id IN
            (SELECT channel_id FROM article WHERE article_id = NEW.article_id)) <> NEW.user_id
        BEGIN
            INSERT INTO notification (type, type_id, article_id, is_read, type_user_id, user_id)
                VALUES ('like', NEW.article_id, NEW.article_id, false, NEW.user_id,
                    (SELECT user_id from channel WHERE channel_id IN
                        (SELECT channel_id FROM article WHERE article_id = NEW.article_id)
                    )
                )
        END;
        """
    )
]

>>>django.db.utils.ProgrammingError: (1064, "You have an error in your SQL syntax; 
check the manual that corresponds to your MariaDB server version for the right syntax 
to use near 'BEGIN\n INSERT INTO notification (type, type_id, article_id, is_re' at line 5")

和

CREATE TRIGGER like_notification AFTER INSERT ON user_likes_article
        FOR EACH ROW
        BEGIN
            DECLARE @user_same Boolean;
            SELECT 1 into @user_same
            FROM channel
            WHERE channel_id IN (select channel_id FROM article where article_id = NEW.article_id)
            AND user_id = NEW.user_id;

            IF @user_same <> 1
            THEN
                INSERT INTO notification (type, type_id, article_id, is_read, type_user_id, user_id,)
                VALUES ('like', NEW.article_id, NEW.article_id, false, NEW.user_id, (
                    SELECT user_id from channel WHERE channel_id IN (
                         SELECT channel_id FROM article WHERE article_id = NEW.article_id)
                    )
            END IF;
        END;

>>>You have an error in your SQL syntax; check the manual that corresponds to your 
MariaDB server version for the right syntax to use near '@user_same Boolean;\n                SELECT 1 into @user_same\n                FRO' at line 4"

我真的不明白为什么它们都不起作用。任何帮助将非常感激！

Answer 1

@variables不是DECLARED。

或者：

DECLARE user_same BOOLEAN;
SELECT 1 INTO user_same WHERE ...

或

SELECT @user_same := 1 WHERE ...

更好的是，这避免了变量的需要。

IF (EXISTS SELECT * FROM ...)

另外，不要使用构造IN ( SELECT ... );通常最好使用WHERE EXISTS ( SELECT * FROM ... )或JOIN ... ON ...。

（修复后可能会出现更多问题。）

Answer 2

另一种简便的方法。

您应在;分隔符之间添加任何符号，以将MySQL语法适当地转换为原始SQL。

CREATE TRIGGER trigger_name BEFORE INSERT ON table
FOR EACH ROW
BEGIN
IF NEW.number <> 'anynumber' AND NEW.number <> 'anynumber'
  THEN
    SET NEW.number = 'anynumber'; --
END IF; --
END

该示例由于破折号而起作用。

Django迁移sql用于条件触发器

2 个答案: