TSQL，刪除基於行指數排

Question

我的表是這樣的.....

---

**AttName**  **Title**  **Count_Index** 

Red    Boys    1 
Red    Girls    2 
Green    Boys    1 
Blue    Boys    1 

我只想要回...因爲我

Red Boys  1 
Red Girls  2 

那有兩個條目的紅色，我想跳過/刪除所有的行，如果他們的計數是隻有1.換句話說，我只對行的興趣，如果他們的計數超過「1」。

Answer 1

嘗試

SELECT * 
    FROM table1 
WHERE AttName IN (SELECT AttName FROM table1 GROUP BY AttName HAVING COUNT(*) > 1) 

SQLFiddle

輸出

| ATTNAME | TITLE | COUNT_INDEX | 
--------------------------------- 
|  Red | Boys |   1 | 
|  Red | Girls |   2 | 

Answer 2

好的，這是測試。在尋找重複項目時，我喜歡使用窗口功能。特別是因爲避免在where子句中進行子選擇，並且從同一個表中進行兩次。相反，所有需要的列已被拉入子查詢中。儘管開窗功能有時可能很昂貴。

Select *, ROW_NUMBER() over (Partition by AttrName Order By AttrName) --probably better to order by whatever the primary key is for consistent results, esepcially if you plan to use this in a delete statement 
From (
    SELECT AttName, title, COUNT(AttrName) over (partition by AttrName) as cnt 
    FROM yourtable 
) as counted 
Where counted.cnt > 1