mysql - 增量变量和存储过程检查重复项的问题

Question

我的程序有问题。我有表 oferty_in 其中包含字段(id、status、...、id_om)。我想要检查具有相同 id_om 的是否存在行的程序。

如果存在，则删除状态 = 'N' 的行(N - 新)。

我的程序几乎可以工作，但我在循环迭代时遇到问题。每次我运行程序时，程序都会删除一半行。我不知道问题出在哪里...

DELIMITER //
CREATE PROCEDURE check_duplicates_oferty_in()
BEGIN
DECLARE n INT DEFAULT 0;
DECLARE i INT DEFAULT 0;
DECLARE v_id_del BIGINT;

SELECT count(*) INTO n FROM oferty_in where status_oferty = 'N';

SET i=0;

WHILE i<n DO 
IF EXISTS (SELECT id_om FROM oferty_in group by id_om having count(*) >= 2 LIMIT i,1) THEN
SELECT id_om INTO v_id_del FROM oferty_in group by id_om having count(*) >= 2 LIMIT i,1;
DELETE from oferty_in where id_om = v_id_del and status_oferty = 'N';
END IF;
SET i=i+1;

END WHILE;
END
//  

我也尝试:

IF EXISTS (SELECT id_om FROM oferty_in group by id_om having count(*) >= 2 LIMIT i,1) THEN
    SELECT id_om INTO v_id_del FROM oferty_in group by id_om having count(*) >= 2 LIMIT i,1;
    DELETE from oferty_in where id_om = v_id_del and status_oferty = 'N';
    SET i=i+1;
    ELSE 
    SET i=i+1;
    END IF;

但是都是一样的。 每次都是半行。当 status = 'N' 时，我使用计数器“i”和 while 循环 在 oferty_in 中的行上逐行迭代。有人知道我做错了什么吗？感谢您的帮助和时间。

Answer 1

当 id_om 重复时，您似乎想要删除 status = 'N' 的行。

I want procedure which check if exist rows with the same id_om. If exist, delete rows where status = 'N' (N - new).

非工作代码通常无助于解释逻辑，所以这就是我要做的。

您绝对不需要为此使用循环结构，也不需要游标:

delete o
    from oferty_in o join
         (select o2.id_om
          from oferty_in o2
          group by o2.id_om
          having count(*) > 1 and sum(status = 'N') > 0
         ) o2
         on o.id_om = o2.id_om
    where o.status = 'N';