遍歷臨時表時獲取記錄值

Question

場景 ：

1. 從一個TableA中選擇記錄
2. 遍歷表值
3. 根據每個記錄的值從另一個表（TableB）中刪除

樣品 ：

DECLARE @CustomerList TABLE (CustomerID bigint) 
INSERT INTO @CustomerList SELECT CustomerID FROM TableA WHERE CustomerID = @ParameterID

WHILE (SELECT COUNT(*) FROM @CustomerList) > 0
BEGIN
DELETE FROM [TableB]
WHERE [CustomerID] = @CustomerList.CustomerID -- challenge
END

挑戰 ：

• 傳遞每個循環的CustomerID值

更新資料

• 想要使用循環的原因是要執行多個delete語句

Answer 1

為什么循環？

Delete From [Table B]
 Where [CustomerID] in (Select CustomerID from TableA where SomeCondition=true)

確定，然后支持多個刪除。 您可以保持表格可變

DECLARE @CustomerList TABLE (CustomerID bigint) 
INSERT INTO @CustomerList SELECT CustomerID FROM TableA WHERE CustomerID = @ParameterID

Delete From [Table B] Where [CustomerID] in (Select CustomerID from @CustomerList)
Delete From [Table C] Where [CustomerID] in (Select CustomerID from @CustomerList)

Answer 2

為什么不使用join，而不是使用join。 像下面這樣。

DELETE t
FROM TableB as t
join @CustomerList as c
on t.CustomerID = C.CustomerID;

Answer 3

我不確定為什么需要臨時表或循環。 聯接應該起作用。

例：

DELETE B
FROM TableB B
INNER JOIN TableA A
  ON B.CustomerID=A.CustomerID
WHERE A.CustomerID = @ParameterID