SQL Server子查詢返回了多個值。 當子查詢跟隨（字符）或子查詢用作表達式時，不允許這樣做

Question

我試圖根據它們的出現更新一些字段。 如果它們只出現一次，我正在更新一些狀態字段。

我目前的代碼如下：

UPDATE table1
SET statusField = 1
WHERE someID = (
               SELECT someID
               FROM table1
               GROUP BY someID HAVING COUNT(*) = 1
               )

這將返回一個錯誤，如標題中的錯誤： Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

還有其他易於閱讀/簡單的解決方案嗎？

Answer 1

使用IN關鍵字而不是equals運算符，如下所示：

UPDATE table1
SET statusField = 1
WHERE someID IN (
           SELECT someID
           FROM table1
           GROUP BY someID HAVING COUNT(*) = 1
           )

使用=要求子查詢返回1個結果。 IN關鍵字適用於列表。

Answer 2

您應該在子選擇中加入表格。 可以使用'in'，但在你的情況下我會使用exists：

UPDATE table1 x
SET statusField = 1
WHERE exists (
               SELECT null
               FROM table1
               WHERE x.someID = someID
               GROUP BY someID 
               HAVING COUNT(*) = 1
               )

為了獲得更好的性能，我會使用這個腳本（sqlserver-2008 +）：

;WITH x as
(
SELECT rc = count() over (partition by someID), statusField
FROM table1
)
UPDATE x
SET statusField = 1
WHERE rc = 1

Answer 3

嘗試這個

使用Top

UPDATE table1
SET statusField = 1
WHERE someID = (
               SELECT TOP 1 someID
               FROM table1
               GROUP BY someID HAVING COUNT(*) = 1
               )

或者你可以使用IN子句

UPDATE table1
SET statusField = 1
WHERE someID IN (
               SELECT someID
               FROM table1
               GROUP BY someID HAVING COUNT(*) = 1
               )