Sql

Question

我有一个 mssql table，格式如下：

ID  |Code   |Name   |Date
1   |01     |A      |2011-01-01 00:01:23
2   |02     |B      |2011-07-01 00:01:23
3   |01     |A      |2011-05-01 00:01:23
4   |01     |A      |2011-07-01 00:01:23
5   |03     |C      |2011-02-01 00:01:23
6   |04     |D      |2011-01-01 00:01:23
7   |03     |C      |2011-01-01 00:01:23
8   |02     |B      |2011-01-01 00:01:23

I need to select unique code with with latest date as follows:

ID  |Code   |Name   |Date
1   |01     |A      |2011-07-01 00:01:23
2   |02     |B      |2011-07-01 00:01:23
3   |03     |C      |2011-02-01 00:01:23
4   |04     |D      |2011-01-01 00:01:23

如何编写 sql 查询来实现此目的？

Answer 1

很简单就是用了Group by Clause..

select ID,Code,Name,MAX(Date) as Date from TableName Group by Id,Code,Name

另一种方式是 CTE 函数

With CTE AS
(
SELECT  row_number() over(partition by Code order by Code) rn
ID,Code,Name,MAX(Date) as Date
FROM TableName 
)

select ID,Code,Name,Date from CTE  where rn = 1

Answer 2

使用 Group BY 并获取 MAX 日期。

SELECT ROW_NUMBER() OVER (ORDER BY Code), Code, Name, MAX(Date)
FROM Table
GROUP BY Code, Name

Answer 3

请将 table 名称放在 "YourTable" 的位置，然后尝试下面的查询。

SELECT ID,CODE,NAME,MAX(DATE)
FROM YourTable
GROUP BY ID,CODE,NAME
ORDER BY CODE,NAME DESC

Answer 4

使用相关子查询：

select t.*
from t
where t.date = (select max(t2.date) from t t2 where t2.code = t.code);

Answer 5

与NOT EXISTS:

select t.* from tablename t
where not exists (
  select 1 from tablename
  where code = t.code abd date > t.date
);

或 ROW_NUMBER():

select t.id, t.code, t.name, t.date
from (
  select *, row_number() over (partition by code order by date desc) rn
  from tablename
) t
where t.rn = 1;

Answer 6

要保持相同的 ID：

SELECT Id, Code, Name, [Date]
FROM
(
    SELECT *
     , ROW_NUMBER() OVER (PARTITION BY Code, Name ORDER BY [Date] DESC, Id) AS Rn
    FROM yourtable
) q
WHERE Rn = 1
ORDER BY Id;

获取新 ID：

SELECT 
 ROW_NUMBER() OVER (ORDER BY MAX([Date]), Code, Name) AS Id, 
 Code, 
 Name, 
 MAX([Date]) AS [Date]
FROM yourtable
GROUP BY Code, Name;

Answer 7

试试这个：

SELECT tbl1.* FROM tbl1 WHERE tbl1.date = (SELECT max(tbl2.date) FROM tbl1 tbl2 WHERE tbl2.code = tbl1.code);

Sql - 如何根据 mssql 中的列生成唯一记录

Sql - How to generate unique record based on column from mssql

tsql

sql-server

sql-server-2008