SELECT First Group - sql

Question

Problem Definition
I have an SQL query that looks like:
SELECT *
FROM table
WHERE criteria = 1
ORDER BY group;
Result
I get:
group | value | criteria
------------------------
A | 0 | 1
A | 1 | 1
B | 2 | 1
B | 3 | 1
Expected Result
However, I would like to limit the results to only the first group (in this instance, A). ie,
group | value | criteria
------------------------
A | 0 | 1
A | 1 | 1
What I've tried
Group By
SELECT *
FROM table
WHERE criteria = 1
GROUP BY group;
I can aggregate the groups using a GROUP BY clause, but that would give me:
group | value
-------------
A | 0
B | 2
or some aggregate function of EACH group. However, I don't want to aggregate the rows!
Subquery
I can also specify the group by subquery:
SELECT *
FROM table
WHERE criteria = 1 AND
group = (
SELECT group
FROM table
WHERE criteria = 1
ORDER BY group ASC
LIMIT 1
);
This works, but as always, subqueries are messy. Particularly, this one requires specifying my WHERE clause for criteria twice. Surely there must be a cleaner way to do this.

Answer 1

You can try following query:-
SELECT *
FROM table
WHERE criteria = 1
AND group = (SELECT MIN(group) FROM table)
ORDER BY value;

Answer 2

If your database supports the WITH clause, try this. It's similar to using a subquery, but you only need to specify the criteria input once. It's also easier to understand what's going on.
with main_query as (
select *
from table
where criteria = 1
order by group, value
),
with min_group as (
select min(group) from main_query
)
select *
from main_query
where group in (select group from min_group);
-- this where clause should be fast since there will only be 1 record in min_group

Answer 3

Use DENSE_RANK()
DECLARE #yourTbl AS TABLE (
[group] NVARCHAR(50),
value INT,
criteria INT
)
INSERT INTO #yourTbl VALUES ( 'A', 0, 1 )
INSERT INTO #yourTbl VALUES ( 'A', 1, 1 )
INSERT INTO #yourTbl VALUES ( 'B', 2, 1 )
INSERT INTO #yourTbl VALUES ( 'B', 3, 1 )
;WITH cte AS
(
SELECT i.* ,
DENSE_RANK() OVER (ORDER BY i.[group]) AS gn
FROM #yourTbl AS i
WHERE i.criteria = 1
)
SELECT *
FROM cte
WHERE gn = 1
group | value | criteria
------------------------
A | 0 | 1
A | 1 | 1