SQL：消息116，級別16，狀態1，第1行只有一個表達式可以在選擇列表中指定當子查詢未與EXISTS引入

Question

請幫助我如何修復了這個問題

消息116，Level 16，State 1，Line 1
當子查詢未與 EXISTS一起引入時，只能在選擇列表中指定一個表達式。

這裏是我的查詢

SELECT a.RegId, 
     a.PropertyThumbnail 
FROM tblPropertyDetail a 
WHERE a.RegId NOT IN 
     (
      SELECT RegId, 
        COUNT(RegId) AS NumOccurrences 
      FROM tblPropertyDetail 
      GROUP BY RegId 
      HAVING (COUNT(RegId) > 1) 
     ) 

Answer 1

刪除此列中的子查詢COUNT(RegId) AS NumOccurrences

SELECT a.RegId, 
     a.PropertyThumbnail 
FROM tblPropertyDetail a 
WHERE a.RegId NOT IN (
       SELECT RegId 
       FROM tblPropertyDetail 
       GROUP BY RegId 
       HAVING (COUNT(RegId) > 1) 
       ) 

使用 NOT IN時

，預計列數由子查詢返回僅僅是一。

或者，你也可以做到這一點使用JOIN

SELECT a.RegId, 
     a.PropertyThumbnail 
FROM tblPropertyDetail a 
     LEFT JOIN 
     (
      SELECT RegId, COUNT(RegId) AS NumOccurrences 
      FROM tblPropertyDetail 
      GROUP BY RegId 
      HAVING (COUNT(RegId) > 1) 
     ) b ON a.RegId = b.RegId 
WHERE b.RegId IS NULL 

Answer 2

在SQLServer2005的+使用CTE與骨料窗函數

;WITH cte AS 
(
    SELECT RegId, PropertyThumbnail, COUNT(*) OVER (PARTITION BY RegId) AS cnt 
    FROM tblPropertyDetail 
) 
    SELECT RegId, PropertyThumbnail 
    FROM cte 
    WHERE cnt <= 1