刪除重複的數據，其中有不同的日期條目保留最早的一個

Question

我有一個表中有一些我想刪除的不正確的數據。

邏輯如下。代碼，名稱和來源相同（如下表中的前三行，我想用最早的日期保留記錄，所以在這種情況下2017-01-02，然後刪除其他兩行。 ？此

DateEntry Code Name  Source 
    2017-01-02 ABCF Blah  SS 
    2017-03-02 ABCF Blah  SS 
    2017-04-02 ABCF Blah  SS  
    2017-03-08 BVFT Andy  SS 
    2017-04-14 BVFT Andy  SS 
    2017-04-20 BVFT Blob  SS 
    2017-04-28 BVFT Blob  SS 
    2017-05-14 BVFT Blob  SS 
    2017-06-02 BVFT Blob  SS 

我想要什麼，

DateEntry Code Name  Source 
    2017-01-02 ABCF Blah  SS 
    2017-03-08 BVFT Andy  SS 
    2017-04-20 BVFT Blob  SS 

Answer 1

通過DateEntry列的升序給由列Code，Name和Source和順序劃分的行數。然後刪除了具有行號的行大於1

查詢

;with cte as(
    select [rn] = row_number() over(
     partition by Code, Name, Source 
     order by DateEntry  
    ), * 
    from your_table_name 
) 
delete from cte 
where rn > 1; 

Find a demo here

Answer 2

您可以使用排序功能ROW_NUMBER與PARTITION BY Code, Name：

WITH Ranked 
AS 
(
    SELECT 
     DateEntry, Code,Name, Source, 
     ROW_NUMBER() OVER(PARTITION BY Code, Name ORDER BY DateEntry) AS RN 
    FROM table1 
) 
SELECT DateEntry, Code,Name, Source 
FROM Ranked 
WHERE RN = 1; 

分級功能將產生每行的行號，組中的第一個是1，最早的那一行。然後過濾器將刪除除了每組的第一行之外的所有內容。

• Demo

結果：

| DateEntry | Code | Name | Source | 
|------------|------|------|--------| 
| 2017-01-02 | ABCF | Blah |  SS | 
| 2017-03-08 | BVFT | Andy |  SS | 
| 2017-04-20 | BVFT | Blob |  SS | 

---

請記住，這實際上不會刪除其他行，這只是一個選擇。

Answer 3

SELECT * FROM (
SELECT 
    *, 
    ROW_NUMBER() OVER(PARTITION BY DateEntry ORDER BY DateEntry DESC) AS rn 
FROM MyTable 
) a 
WHERE rn = 1 

Answer 4

與此

;with cte as (
SELECT *,ROW_NUMBER() OVER(PARTITION BY Code,Name,Source ORDER BY DateEntry DESC) AS rnum 
FROM MyTable 
) 
delete from cte where rnum>1 

Answer 5

你應該ROW_NUMBER()功能通過SubQuery形式嘗試：

SELECT DateEntry, 
     Code, 
     Name, 
     Source 
FROM 
(
    SELECT *, 
      ROW_NUMBER() OVER(PARTITION BY Code, 
              Name, 
              Source ORDER BY dateentry) rn 
    FROM <table_name> 
) a 
WHERE rn = 1; 

結果：

| DateEntry | Code | Name | Source | 
|------------|------|------|--------| 
| 2017-01-02 | ABCF | Blah |  SS | 
| 2017-03-08 | BVFT | Andy |  SS | 
| 2017-04-20 | BVFT | Blob |  SS | 

Answer 6

WITH t1 AS 
(
SELECT ROW_NUMBER() OVER (PARTITION BY Code,Name,Source ORDER BY DateEntry) AS 
'Rank',Code,Name,Source 
FROM TABLE 
) 
DELETE FROM t1 WHERE t1.Rank>1