選擇每個代碼

Question

我已經得到了郵件存儲 這樣一個表中的一行： codMsg，消息，anotherCod

1, 'hi', 1 
2, 'hello', 1 
3, 'wasup', 1 
4, 'yo', 2 
5, 'yeah', 2 
6, 'gogogo', 3 

我在想，如果可以選擇每個anotherCod

的頂部1

我想到：

1, 'hi', 1 
4, 'yo', 2 
6, 'gogogo', 3 

我想整條生產線，而不僅僅是anotherCod的數量，所以按不應該工作

Answer 1

select mytable.* 
from mytable 
join (select min(codMsg) as codMsg, anotherCod from mytable group by 2) x  
    on mytable.codMsg = x.codMsg 

Answer 2

SELECT 
    * 
FROM 
    myTable 
WHERE 
    codMSG = (SELECT MIN(codMsg) FROM myTable AS lookup WHERE anotherCod = myTable.anotherCod) 

Answer 3

的SQL Server 2005+，甲骨文：

SELECT codMsg, 
     message, 
     anotherCod 
FROM 
(
    SELECT codMsg, 
      message, 
      anotherCod, 
      RANK() OVER (PARTITION BY anotherCod ORDER BY codMsg ASC) AS Rank 
    FROM mytable 
) tmp 
WHERE Rank = 1