I want to get minimum of starttime of each id. But I'm not able to achieve it using min function. How to solve it? - sql

Question

Table:
id | starttime | grade
-------------------------
1 | 4PM | A
1 | 5PM | C
2 | 2PM | A
2 | 3PM | B
In output I should get all the ids that have minimum starttime with all the columns.
For the above table output should be like this:
id | starttime | grade
-------------------------
1 | 4PM | A
2 | 2PM | A

Answer 1

Using top with ties and row_number() to get the minimum starttime for each id.
select top (1) with ties *
from t
order by row_number() over (partition by id order by starttime);
rextester demo: http://rextester.com/RJVT1405
returns:
+----+-----------+-------+
| id | starttime | grade |
+----+-----------+-------+
| 1 | 4PM | A |
| 2 | 2PM | A |
+----+-----------+-------+

Answer 2

In SQL Server, use top with ties:
select top (1) with ties t.*
from t
order by starttime;
TOP (1) only returns one row. TOP (1) WITH TIES returns all rows that have the same key value as in the first row specified by the ORDER BY.

Answer 3

You can use group by:
with minTimes (id, startTime) as
(
select id, min(startTime) from myTable
group by id
)
select t1.*
from myTable t1
inner join minTimes t2 on t1.id = t2.id and t1.startTime = t2.startTime

Answer 4

;WITH cte(id,starttime, grade)
AS
(
SELECT 1 , '4PM','A' Union all
SELECT 1 , '5PM','C' Union all
SELECT 2 , '2PM','A' Union all
SELECT 2 , '3PM','B'
)
,Final AS (
SELECT *
,Row_Number() OVER (
PARTITION BY MinStartTime ORDER BY MinStartTime
) Seq
FROM (
SELECT id
,CAST(starttime AS TIME) AS starttime
,MIN(CAST(starttime AS TIME)) OVER (
PARTITION BY ID ORDER BY starttime
) AS MinStartTime
,grade
FROM cte
) Dt
)
SELECT id
,CONVERT(VARCHAR(15), MinStartTime, 100) AS starttime
,grade
FROM final
WHERE Seq = 1
ORDER BY 1