从具有两个父级的子表中删除，而无需在 sql server 中进行级联删除答案

【问题标题】：Delete from child table with two parents without cascade delete in sql server从具有两个父级的子表中删除，而无需在 sql server 中进行级联删除
【发布时间】：2019-11-30 23:11:01
【问题描述】：

我需要你的指导。我创建了一个脚本来分别从 3 个表中删除。意思是当我创建脚本时是从 table3 (child) 中删除然后从 2（子）删除，然后从 table1（父）删除我在使用 Table3 时遇到问题，因为 table2 对 table2 和 table1 所以在删除 table2 之前我无法删除它如果我先删除 table2，那么我会丢失用于查找行的参考 delete 然后我从 table3 和 table1 中删除 0。

脚本如下所示

DELETE FROM table3 t3
        INNER JOIN table1 t1 ON t3.t1ID = t1.t1ID
        INNER JOIN table2 t2 i ON t2.t1ID = t1.t1ID
        WHERE t3.t1ID IN(
         SELECT DISTINCT t1.t1ID            
                    FROM t2     
                        WHERE (
                              (t2.t2ID IS NULL AND t1.LastDate <@UpDate )))

上面删除0，因为我删除表2之前删除

DELETE 
        FROM table2 t2 
         INNER JOIN table1 t1 on t2.T1ID =t1.t1ID 
         WHERE t2.t1ID IN(
         SELECT DISTINCT t1.T1ID            
                    FROM t2                 
                        WHERE (
                              (t2.t2ID is null and t1.LastDate <@UpDate <@UpDate )))

它也不会从 table1 中删除，因为脚本会查找 table2 中不存在的位置

DELETE 
        FROM table1 t1
        INNER JOIN table2 t2 i ON t2.t1ID = t1.t1ID
        WHERE t1.t1ID IN(
         SELECT DISTINCT t1.t1ID        
                    FROM t2 
                        WHERE (
                              (t2.t2 IS NULL ANDt1.LastDate <@UpDate)))

【问题讨论】：

标签： sql sql-server parent-child sql-delete cascade

【解决方案1】：

试试这样的：

DECLARE @RowsToDelete TABLE
(
    RowsToDeleteID int IDENTITY(1,1) PRIMARY KEY,
    Table1ID int,
    Table2ID int,
    Table3ID int
);

INSERT @RowsToDelete (Table1ID, Table2ID, Table3ID)
SELECT DISTINCT t1.t1ID, t2.t2ID, t3.t3ID 
FROM table3 AS t3
INNER JOIN table1 AS t1 
ON t3.t1ID = t1.t1ID
INNER JOIN table2 AS t2 
ON t2.t1ID = t1.t1ID
WHERE t2.t2ID IS NULL 
AND t1.LastDate < @UpDate;

DELETE table2
WHERE EXISTS (SELECT 1 FROM @RowsToDelete AS rtd WHERE rtd.Table2ID = t2ID);

DELETE table1
WHERE EXISTS (SELECT 1 FROM @RowsToDelete AS rtd WHERE rtd.Table1ID = t1ID);

DELETE table3
WHERE EXISTS (SELECT 1 FROM @RowsToDelete AS rtd WHERE rtd.Table3ID = t3ID);

还没有桌子等可以尝试，但看起来应该没问题。

我在这里还假设这些行在您执行此操作时可能不会发生变化，否则您可能会遇到竞争条件。

【讨论】：