使用 Group By 删除重复项

Question

我有一个类似的问题No duplicates in SQL query

请find here the sqlFiddle

我有这个：

+----------+-----------------+----------+----------+-----------+----------+
| TAFIELDA |   DESCRIPTION   | TBFIELDA | TBFIELDB | DOCNUMBER | TCFIELDB |
+----------+-----------------+----------+----------+-----------+----------+
|     1000 | some data       |     2000 |     1000 |       525 |     2000 |
|     1001 | some other data |     2000 |     1001 |       525 |     2000 |
+----------+-----------------+----------+----------+-----------+----------+

预期结果：

+----------+-----------------+----------+----------+-----------+----------+
| TAFIELDA |   DESCRIPTION   | TBFIELDA | TBFIELDB | DOCNUMBER | TCFIELDB |
+----------+-----------------+----------+----------+-----------+----------+
|     1001 | some other data |     2000 |     1001 |       525 |     2000 |
+----------+-----------------+----------+----------+-----------+----------+

我只需要DocNumber = 525 中的最高TAFIELDA 值，所以我这样做了：

SELECT max(tAFieldA) tAFieldA,DocNumber
FROM TABLEA A
INNER JOIN TABLEB B ON A.TAFIELDA = B.TBFIELDB
INNER JOIN TABLEC C ON B.tBFieldA = C.tCFieldB
where DocNumber = 525
group by (DocNumber)

该查询只返回我正在查找的行，问题是如果我添加另一个不能汇总的字段，例如Description，我会再次获得几条记录。

¿我怎样才能在 sample DB 的所有字段中为每个 DocNumber 获取一条记录？

Answer 1

使用子查询

SELECT * FROM 
(
SELECT *
      ,ROW_NUMBER() OVER (PARTITION BY DOCNUMBER ORDER BY tAFieldA DESC) rn
FROM TABLEA A
INNER JOIN TABLEB B ON A.TAFIELDA = B.TBFIELDB
INNER JOIN TABLEC C ON B.tBFieldA = C.tCFieldB
) Sub 
WHERE rn = 1

使用 CTE

;WITH CTE
 AS
   (
    SELECT *
          ,ROW_NUMBER() OVER (PARTITION BY DOCNUMBER ORDER BY tAFieldA DESC) rn
    FROM TABLEA A
    INNER JOIN TABLEB B ON A.TAFIELDA = B.TBFIELDB
    INNER JOIN TABLEC C ON B.tBFieldA = C.tCFieldB
   )
 SELECT * FROM CTE
 WHERE rn = 1

Working SQL FIDDLE

Answer 2

使用子查询：

SELECT *
FROM TABLEA A
INNER JOIN TABLEB B ON A.TAFIELDA = B.TBFIELDB
INNER JOIN TABLEC C ON B.tBFieldA = C.tCFieldB
WHERE TAFIELDA IN (
  SELECT max(tAFieldA)
    FROM TABLEA A
   INNER JOIN TABLEB B ON A.TAFIELDA = B.TBFIELDB
   INNER JOIN TABLEC C ON B.tBFieldA = C.tCFieldB
   WHERE DocNumber = 525
   GROUP BY (DocNumber)
  )

Answer 3

select a.* ,b.* ,c.* 
from tablea a
inner join tableb b on a.tafielda = b.tbfieldb
inner join tablec c on b.tbfielda = c.tcfieldb
where (tafielda,docnumber) in
    (
        select max(tafielda) tafielda,docnumber
        from tablea a
        inner join tableb b on a.tafielda = b.tbfieldb
        inner join tablec c on b.tbfielda = c.tcfieldb
        where docnumber = 525
        group by (docnumber)
    )