Question

I am trying to write a query for SQL Server 2005 but I can’t figure out how to do it. I have a table with the following fields:

MessageID int
CategoryID int
Priority tinyint
MessageText NVARCHAR(MAX)

I need a query that will return * for each row that has the highest priority within a Category. For example, if I had the following data:

MessageID, CategoryID, Priority, MessageText
1, 100, 1, Error #1234 occurred
2, 100, 2, Error #243 occurred
3, 100, 3, Error #976 occurred
4, 200, 4, Error #194 occurred
5, 200, 1, Error #736 occurred
6, 300, 3, Error #54 occurred
7, 300, 2, Error #888 occurred

then the result would be:

MessageID, CategoryID, Priority, MessageText
3, 100, 3, Error #976 occurred
4, 200, 4, Error #194 occurred
6, 300, 3, Error #54 occurred

Notice that it returns one row per category, and that it is the row which had the highest priority for that Category.

Can anyone tell me how I can write this query?

Answer 1

Verified:

SELECT     highest_priority_messages.* FROM (     SELECT     m.MessageID     , m.CategoryID     , m.Priority     , m.MessageText     , Rank() OVER          (PARTITION BY m.CategoryID ORDER BY m.Priority DESC) AS p_rank     FROM [Message] m     GROUP BY          m.CategoryID          , m.Priority         , m.MessageID         , m.MessageText ) highest_priority_messages WHERE      p_rank = 1