Select Distinct Records for min date - sql

Question

I Have a query where In I need to select all the distinct ID's from the table, also need to select only the min(date) so that I get records that were inserted 1st and not ID's for all dates.
Basically this is what I am looking for -
Table 1 || Table 2-
ID || ID Date
1 || 1 11/11/2010
1 || 1 10/11/2010
3 || 3 12/01/2010
4 || 4 01/01/2010
4 || 4 02/01/2010
So i need to get all records from Table 2(table1.ID=table2.ID) which has the Minimum Date along with that ID
Result here would be
1 10/11/2010
3 12/01/2010
4 01/01/2010
Here is my query
select u.firstName,u.lastName ,count(*) as theCount
from tbl_appts_change_log c,tbl_appts a, tbl_users u
where c.appt_id=a.ID
and c.user_id=u.userID
and c.appt_id in ( select c.appt_id,min(c.date) from tbl_appts_change_log c, tbl_appts a
where c.appt_id=a.ID
and a.satellite_id='160' GROUP BY c.appt_id)
group by u.firstName,u.lastName
order by count(*) desc,u.firstName,u.lastName

Answer 1

maybe:
select u.firstName,u.lastName ,count(*) as theCount
from tbl_appts_change_log c
INNER JOIN tbl_appts a on c.appt_id=a.ID
INNER JOIN tbl_users u on c.user_id=u.userID
INNER JOIN ( select c.appt_id,min(c.date) as LastDate
from tbl_appts_change_log c
INNER JOIN tbl_appts a on c.appt_id=a.ID
Where a.satellite_id='160' GROUP BY c.appt_id) d
on c.appt_id = d.appt_id and c.date = d.LastDate
group by u.firstName,u.lastName
order by count(*) desc,u.firstName,u.lastName

Answer 2

I am ignoring your code as it seems to be a completely different scenario from what you have described in your question i.e Table1 and Table2. If all you want is the minimum date for each ID all you need is
SELECT T1.ID, MIN(T2.Date)
FROM Table1 T1
JOIN Table2 T2 ON T1.ID = T2.ID
GROUP BY T1.ID
But i am guessing what you really wanted was something like this?
Table 1 || Table 2-
ID || ID Date Desc
1 || 1 11/11/2010 AAA
1 || 1 10/11/2010 BBB
3 || 3 12/01/2010 CCC
4 || 4 01/01/2010 DDD
4 || 4 02/01/2010 EEE
And the expected result
1 10/11/2010 BBB
3 12/01/2010 CCC
4 01/01/2010 DDD
This is slightly more complicated than just doing a group by, and there are two ways to solve it. You could try both and see which one performs best
Method 1 : Using Row number
;WITH ResultCTE AS
(
SELECT T2.ID, T2.Date, T2.Desc,
RowNumber = ROW_NUMBER() OVER(PARTITION BY T2.ID ORDER BY T2.Date ASC)
FROM Table1 T1
JOIN Table2 T2 ON T1.ID = T2.ID
)
SELECT ID, Date, Desc
FROM ResultCTE
WHERE RowNumber = 1
Method 2: Nested query
;WITH ResultCTE AS
(
SELECT T2.ID, MIN(T2.Date) AS Date
FROM Table1 T1
JOIN Table2 T2 ON T1.ID = T2.ID
GROUP BY T2.ID
)
SELECT T.ID, T.Date, T.Desc
FROM Table2 T
JOIN ResultCTE R
ON R.ID = T.ID AND R.Date = T.Date

Answer 3

SELECT u.firstName,
u.lastName ,
COUNT(*) AS theCount
FROM tbl_appts_change_log c,
tbl_appts a,
tbl_users u
WHERE c.appt_id=a.ID
AND c.user_id =u.userID
AND a.satellite_id = '160'
AND c.date = (SELECT MIN(ci.date)
FROM tbl_appts_change_log ci,
tbl_appts ai
WHERE ci.appt_id = ai.ID
AND ci.appt_id = c.appt_id
AND ai.satellite_id= a.satellite_id
)
GROUP BY u.firstName,
u.lastName
ORDER BY COUNT(*) DESC,
u.firstName,
u.lastName

Answer 4

select u.firstName,u.lastName,count(*) as theCount,cm.MinDate
from (
select c.appt_id,min(c.date) as MinDate
from tbl_appts_change_log c, tbl_appts a
where c.appt_id=a.ID
and a.satellite_id='160'
GROUP BY c.appt_id
) cm
inner join tbl_appts_change_log c on cm.appt_id = c.appt_id and cm.MinDate = c.date
inner join tbl_appts a on c.appt_id=a.ID
inner join tbl_users u on c.user_id=u.userID
group by u.firstName,u.lastName
order by count(*) desc,u.firstName,u.lastName

Answer 5

If what you are looking for is-
Table 1 || Table 2-
ID || ID Date
1 || 1 11/11/2010
1 || 1 10/11/2010
3 || 3 12/01/2010
4 || 4 01/01/2010
4 || 4 02/01/2010
Try using this:
SELECT DISTINCT i1.id, i2.dt
FROM Table1 i1 JOIN (SELECT id, min(date) dt FROM Table2 GROUP BY id) i2
ON i1.id=i2.id

Answer 6

Is this what you're after?
select u.firstName,u.lastName ,count(*) as theCount
from tbl_appts_change_log c,tbl_appts a, tbl_users u
where c.appt_id=a.ID
and c.user_id=u.userID
and a.satellite_id = '160'
and c.date = (
select min(date)
from tbl_appts_change_log c, tbl_appts a
where c.appt_id = a.id
and a.satellite_id = '160'
)
group by u.firstName,u.lastName
order by count(*) desc,u.firstName,u.lastName