如果条件未按预期运行，则MySQL AFTER DELETE触发器

Question

我有一个名为Buyer_invoice_payments的表（ Buyer_inv_id （PK）， payment_id （PK）， paid_amt ）。 删除该表中的记录后，需要根据payment_id的计数执行两项操作

这是关于AFTER DELETE TRIGGER的MySQL查询，

BEGIN

    IF ((SELECT COUNT(payment_id) FROM buyer_invoice_payments BIP WHERE BIP.payment_id = OLD.payment_id) > 1) THEN

        # a certain operation

    ELSE

        # a certain operation

    END IF;

END

我的问题是，即使COUNT（payment_id）大于1，此条件也总是会失败，这意味着它将转到else块。

但是，如果我改变OLD.payment_id在if条件payment_id这将工作， 但是当COUNT（payment_id）等于1，也转到if块（不else块）

我尝试了几种不同的更改if条件的方法，但没有一种能起作用，这是我尝试过的几种方法（仅显示if条件）

#1
IF ((SELECT COALESCE(COUNT(payment_id),0) FROM buyer_invoice_payments BIP WHERE BIP.payment_id = OLD.payment_id) > 1) THEN

#2
IF (SELECT (COUNT(payment_id) != 1) FROM buyer_invoice_payments BIP WHERE BIP.payment_id = OLD.payment_id) THEN

有人可以帮我弄清楚我做错了什么。

Answer 1

我不同意，这就是原因。

drop trigger if exists Tafter_aff_purchases;
delimiter //
CREATE DEFINER=`root`@`localhost` TRIGGER `Tafter_aff_purchases` AFTER delete ON `aff_purchases` 
FOR EACH ROW 
BEGIN    
    #insert into errors (msg) values (concat('old.id = ',old.id));
IF ((SELECT COUNT(id) FROM aff_purchases BIP WHERE BIP.id = OLD.id) > 0 ) THEN
        insert into errors (msg) values ('Operation1 carried out');
    ELSE
        insert into errors (msg) values ('Operation2 carried out');
    END IF;
END //

delimiter ;

MariaDB [sandbox]> truncate table aff_purchases;
Query OK, 0 rows affected (0.27 sec)

MariaDB [sandbox]> insert into aff_purchases
    -> (id , affiliate_id , order_id , payout , ip_address , date_submitted) values
    -> (1,1,1,10,null,'2017-01-01'),
    -> (1,1,1,20,null,'2017-02-01'),
    -> (1,1,1,30,null,'2017-03-01');
Query OK, 3 rows affected (0.02 sec)
Records: 3  Duplicates: 0  Warnings: 0

MariaDB [sandbox]>
MariaDB [sandbox]> truncate table errors;
Query OK, 0 rows affected (0.27 sec)

MariaDB [sandbox]> delete from aff_purchases where id = 1 and payout = 10;
Query OK, 1 row affected (0.02 sec)

MariaDB [sandbox]> select * from errors;
+------------------------+----+
| msg                    | id |
+------------------------+----+
| Operation1 carried out |  1 |
+------------------------+----+
1 row in set (0.00 sec)

MariaDB [sandbox]> select * from aff_purchases;
+------+--------------+----------+--------+------------+----------------+
| id   | affiliate_id | order_id | payout | ip_address | date_submitted |
+------+--------------+----------+--------+------------+----------------+
|    1 |            1 |        1 |     20 | NULL       | 2017-02-01     |
|    1 |            1 |        1 |     30 | NULL       | 2017-03-01     |
+------+--------------+----------+--------+------------+----------------+
2 rows in set (0.00 sec)

MariaDB [sandbox]> delete from aff_purchases where id = 1 and payout = 20;
Query OK, 1 row affected (0.02 sec)

MariaDB [sandbox]> select * from errors;
+------------------------+----+
| msg                    | id |
+------------------------+----+
| Operation1 carried out |  1 |
| Operation1 carried out |  2 |
+------------------------+----+
2 rows in set (0.00 sec)

MariaDB [sandbox]> select * from aff_purchases;
+------+--------------+----------+--------+------------+----------------+
| id   | affiliate_id | order_id | payout | ip_address | date_submitted |
+------+--------------+----------+--------+------------+----------------+
|    1 |            1 |        1 |     30 | NULL       | 2017-03-01     |
+------+--------------+----------+--------+------------+----------------+
1 row in set (0.00 sec)

MariaDB [sandbox]> delete from aff_purchases where id = 1 and payout = 30;
Query OK, 1 row affected (0.03 sec)

MariaDB [sandbox]> select * from errors;
+------------------------+----+
| msg                    | id |
+------------------------+----+
| Operation1 carried out |  1 |
| Operation1 carried out |  2 |
| Operation2 carried out |  3 |
+------------------------+----+
3 rows in set (0.00 sec)

MariaDB [sandbox]> select * from aff_purchases;
Empty set (0.00 sec)

我正在使用错误表来捕获触发器中发生的事情。 您应该能够看到每个删除操作都会在错误表中触发相应的味精。

Answer 2

最终，我发现了我一直在做的错误。 如果使用OLD.payment_id，则在AFTER DELETE触发器中使用“> 1” ，该特定ID已被删除，而COUNT与其余ID一起获得。 我的目的是获取具有相同ID（包括已删除的ID）的记录的计数。 解决方案是使用“> 0”