問題描述

我最近遇到了一種情況，我需要從表中刪除一些行并拼錯列名.沒有拋出錯誤，所有行都從表中刪除.這是重現該問題的腳本.

I recently had a situation where I needed to delete some rows from a table and mis-spelt a column name. There was no error thrown and ALL the rows were deleted from the table. Here is a script that reproduces the issue.

有一個 Order 表，有四個帶有 OrderID 的訂單.有一個帶有一個 ItemID 的 LIST_TO_DELETE 表.

There is an Order table with four orders with OrderID. There is a LIST_TO_DELETE table with one ItemID.

我應該用過

DELETE TOP(1) FROM #Orders WHERE OrderID IN (SELECT ItemID FROM #LIST_TO_DELETE  )

我用了

DELETE TOP(1) FROM #Orders WHERE OrderID IN (SELECT OrderID FROM #LIST_TO_DELETE  )

這導致 #Orders 表中的所有行都被刪除，而我只想刪除一個.

This caused all rows in the #Orders table to be deleted when I only meant to delete one.

CREATE TABLE #Orders (OrderID INT, OrderName VARCHAR(100))
INSERT INTO #Orders(OrderID, OrderName) VALUES (1,'Order One'),(2,'Order Two'),(3,'Order Three'), (4,'Order Four')

CREATE TABLE #LIST_TO_DELETE (ItemID INT);INSERT INTO #LIST_TO_DELETE(ItemID) VALUES (1)

DECLARE @rowcount INT = 1
WHILE @rowcount > 0 
BEGIN
    DELETE TOP(1) FROM #Orders WHERE OrderID IN (SELECT OrderID FROM #LIST_TO_DELETE  )
    SET @rowcount = @@rowcount
END 

SELECT * FROM #Orders

DROP TABLE #Orders
DROP TABLE #LIST_TO_DELETE

在我的原始代碼中，Orders 表是真實的，而 LIST_TO_DELETE 是一個表變量，但使用什么表類型似乎沒有區別.如果我使用除 OrderID 或 ItemID 之外的任何列名，我會收到錯誤

In my original code, the Orders table was real and LIST_TO_DELETE was a table variable but it seems to make no difference what table type is used. If I use any column name apart from OrderID or ItemID, I get an error

DELETE TOP(1) FROM #Orders WHERE OrderID IN (SELECT OtherID FROM #LIST_TO_DELETE  )
 Invalid column name 'OtherID'

為什么這段代碼會這樣?

Why did this code behave this way?

推薦答案

閱讀文章以了解正在發生的事情:在子查詢中限定列名

Read the article to understand what is happening: Qualifying Column Names in Subqueries

一般規則是語句中的列名由同一級別的 FROM 子句中引用的表隱式限定.如果子查詢的 FROM 子句中引用的表中不存在列，則該列由外部查詢的 FROM 子句中引用的表隱式限定.

The general rule is that column names in a statement are implicitly qualified by the table referenced in the FROM clause at the same level. If a column does not exist in the table referenced in the FROM clause of a subquery, it is implicitly qualified by the table referenced in the FROM clause of the outer query.

這篇關于WHERE IN (SELECT NonExistingColumnName) 導致意外行為的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！