SQL Server Selecting Records with most recent date time

Question

I have a table as below:

MyJob|   MyKey  |MyCode|MyDate| MyTime 
----------------------------------       
q183b| 0131081a |  24  |100315| 9:37        
q183b| 01         


        

Answer 1

First combine the date + time columns into a datetime so it's easy to order them. It's been a while since I used Sql Server, but the row_number() function and partitioning is an easy way to find the max of one column grouped by another - the partition clause is similar to a group by.

select t.* 
from
(
    select t.MyKey, t.MyDateTime
    , row_number() over 
         (partition by t.mykey order by t.MyDateTime desc) as keyOrderNbr
    from table t
) A
inner join table t
    on A.MyKey = t.MyKey 
    and A.MyDateTime = t.MyDateTime
where A.keyOrderNbr = 1

Answer 2

Firstly, you will need to convert your date char into a date field so that you can order by it. Then what you can do is:

SELECT DISTINCT *
FROM MyTable
WHERE MyTable.MyDate =
(
    SELECT MAX(Sub_MyTable.MyDate)
    FROM MyTable 
    WHERE MyTable.MyKey = Sub_MyTable.MyKey
);

Now remember, the MAX(MyDate) and other references to MyDate won't do what you require unless you turn the field into a date field. I suggest creating your own function to convert the char field into a date field.

If you try to order by the MyDate field as it is, you will have the results sorted in alphabetical order since it's a string.

If the time part is important in the results then you can combine the two as suggested by @jeff.