Question

Student_No Modified_ON StatusID 
1234       1 Nov 2017   1       
1234       2 Nov 2017   2       
1235       1 Nov 2017   1        
1235       2 Nov 2017   1        
1235       3 Nov 2017   3   
1236       1 Nov 2017   1
1236       3 Nov 2017   2   
1237       3 Nov 2017   3

预期的O / p

Student_No Modified_ON StatusID 
1234       2 Nov 2017   2  
1236       3 Nov 2017   2

我需要所有最新（最高日期）记录，其中StatusID从1变为2

Answer 1

根据您的输出，您需要group by max功能聚合

SELECT Student_No,
       MAX(Modified_ON) [Modified_ON],
       MAX(StatusID) [StatusID]
FROM
(
    SELECT *
    FROM <TABLE>
    WHERE StatusID = 2
          AND Student_No IN
    (
        SELECT Student_No
        FROM <TABLE>
        WHERE StatusID = 1
    )
) AA
GROUP BY Student_No;

以上SQL脚本将返回

Student_No  Modified_ON StatusID
1234        2 Nov 2017  2
1236        3 Nov 2017  2

Answer 2

使用多个查询和if-else子句执行此操作：

SELECT (
CASE WHEN ( (
  SELECT StatusID
  FROM students
  ORDER BY `Modified_ON`  DESC
  LIMIT 1
  ) = 1)
THEN  
  ( SELECT Student_No
  FROM students
  ORDER BY `Modified_ON`  DESC
  LIMIT 1 )
  ELSE (
  SELECT Student_No
  FROM students
      WHERE StatusID = 2 and Student_No in (
      SELECT Student_No
      FROM students
      WHERE StatusID = 1 
  )
  ORDER BY `Modified_ON`  DESC LIMIT 1
  ) 
  END )
FROM students

请参阅mysql-fiddle：http://sqlfiddle.com/#!9/c601d9/2

Answer 3

使用窗口函数我们得到预期的结果

;With cte(Student_No, Modified_ON, StatusID )
AS
(
SELECT 1234,'1 Nov 2017',   1 UNION ALL       
SELECT 1234,'2 Nov 2017',   2 UNION ALL      
SELECT 1235,'1 Nov 2017',   1 UNION ALL       
SELECT 1235,'2 Nov 2017',   1 UNION ALL       
SELECT 1235,'3 Nov 2017',   3 UNION ALL  
SELECT 1236,'1 Nov 2017',   1 UNION ALL
SELECT 1236,'3 Nov 2017',   2 UNION ALL  
SELECT 1237,'3 Nov 2017',   3
)
    SELECT Student_no, 
       Modified_on, 
       Statusid 
FROM   (SELECT Student_no, 
               Max(Modified_on) 
                 OVER( 
                   partition BY Student_no 
                   ORDER BY Modified_on DESC) Modified_ON, 
               Statusid 
        FROM   
                   Cte 
                WHERE  Statusid IN( 1, 2 ))dt2 
WHERE  dt2.Statusid = 2

结果

Student_no  Modified_on Statusid
----------------------------------
1234        2 Nov 2017   2
1236        3 Nov 2017   2

Answer 4

我还有代码但格式不正确，因此Stackflow不允许它。您可以考虑我已实施的以下逻辑。

逻辑：通过唯一编号，Status_Id和按日期排序描述创建SR编号

使用所需的where子句

选择ROw_Number和Rank_Number以选择上面的数据

SQL Statuswise数据选择

4 个答案: