Question

Given 2 tables called “table1” and “table1_hist” that structurally resemble this:

TABLE1
id  status  date_this_status
1   open    2008-12-12
2   closed  2009-01-01
3   pending 2009-05-05
4   pending 2009-05-06
5   open    2009-06-01


TABLE1_hist
id  status  date_this_status
2   open    2008-12-24
2   pending 2008-12-26
3   open    2009-04-24
4   open    2009-05-04

With table1 being the current status and table1_hist being a history table of table1, how can I return the rows for each id that has the earliest date. In other words, for each id, I need to know it’s earliest status and date.

EXAMPLE:

For id 1 earliest status and date is open and 2008-12-12.
For id 2 earliest status and date is open and 2008-12-24.

I’ve tried using MIN(datetime), unions, dynamic SQL, etc. I’ve just reached tsql writers block today and I’m stuck.

Edited to add: Ugh. This is for a SQL2000 database, so Alex Martelli’s answer won’t work. ROW_NUMBER wasn’t introduced until SQL2005.

Answer 1

The following code sample is completely self-sufficient, just copy and paste it into a management studio query and hit F5 =)

DECLARE @TABLE1 TABLE
        (
        id                  INT,
        status              VARCHAR(50),
        date_this_status    DATETIME
        )

DECLARE @TABLE1_hist TABLE
        (
        id                  INT,
        status              VARCHAR(50),
        date_this_status    DATETIME
        )

--TABLE1
INSERT  @TABLE1
SELECT  1,  'open',     '2008-12-12'    UNION ALL
SELECT  2,  'closed',   '2009-01-01'    UNION ALL
SELECT  3,  'pending',  '2009-05-05'    UNION ALL
SELECT  4,  'pending',  '2009-05-06'    UNION ALL
SELECT  5,  'open',     '2009-06-01'

--TABLE1_hist
INSERT  @TABLE1_hist
SELECT  2,  'open',     '2008-12-24'    UNION ALL
SELECT  2,  'pending',  '2008-12-26'    UNION ALL
SELECT  3,  'open',     '2009-04-24'    UNION ALL
SELECT  4,  'open',     '2009-05-04'

SELECT      x.id,
            ISNULL(y.[status], x.[status])                  AS [status],
            ISNULL(y.date_this_status, x.date_this_status)  AS date_this_status
FROM        @TABLE1 x
LEFT JOIN   (
            SELECT      a.*
            FROM        @TABLE1_hist a
            INNER JOIN  (
                        SELECT      id,
                                    MIN(date_this_status) AS date_this_status
                        FROM        @TABLE1_hist
                        GROUP BY    id
                        ) b
                    ON  a.id = b.id
                    AND a.date_this_status = b.date_this_status
            ) y
        ON  x.id = y.id