Query only the first detail record for each master record

linq-to-sql, sql

Solution

Using Sql Server 2005+ you can try (Full example)

DECLARE @owner_tbl TABLE(
        [owner] VARCHAR(50)
)

DECLARE @auto_tbl TABLE(
        [owner] VARCHAR(50),
        [auto] VARCHAR(50),
        [year]VARCHAR(4)
)

INSERT INTO @owner_tbl SELECT 'john'
INSERT INTO @owner_tbl SELECT 'james'
INSERT INTO @owner_tbl SELECT 'jeff'        

INSERT INTO @auto_tbl SELECT 'john','corvette','1968'
INSERT INTO @auto_tbl SELECT 'john','prius','2008'
INSERT INTO @auto_tbl SELECT 'james','f-150','2004'
INSERT INTO @auto_tbl SELECT 'james','cadillac','2002'
INSERT INTO @auto_tbl SELECT 'james','accord','2009'
INSERT INTO @auto_tbl SELECT 'jeff','tesla','2010'
INSERT INTO @auto_tbl SELECT 'jeff','hyundai','1996'

;WITH Autos AS(
        SELECT  *,
                ROW_NUMBER() OVER(PARTITION BY a.owner ORDER BY a.year) ROWID
        FROM    @auto_tbl a
)
SELECT  *
FROM    Autos
WHERE   ROWID = 1
ORDER BY owner

Problem

If I have the following master-detail relationship: ``` owner_tbl auto_tbl --------- -------- owner ---> owner auto year ``` And I have the following table data: ``` owner_tbl auto_tbl --------- -------- john john, corvette, 1968 john, prius, 2008 james james, f-150, 2004 james, cadillac, 2002 james, accord, 2009 jeff jeff, tesla, 2010 jeff, hyundai, 1996 ``` Now, I want to perform a query that returns the following result: ``` john, corvette, 1968 jeff, hyundai, 1996 james, cadillac, 2002 ``` The query should join the two tables, and sort all the records on the "year" field, but only return the first detail record for each master record. I know how to join the tables and sort on the "year" field, but it's not clear how (or if) I might be able to only retrieve the first joined record for each owner. Three related questions: - Can I perform this kind of query using LINQ-to-SQL? - Can I perform the query using T-SQL? - Would it be best to just create a stored procedure for the query given its likely complexity?

Original source