SQL: Select lowest value that doesn't already exist - sql

Question

In TableA I have an int column.
Is it possible using only a select statement to select the minimum value in the column that DOES NOT EXIST and is greater then 0?
For example, if the col has the values 1,2,9 the select statement will return 3.
If the col has 9,10,11 it will return 1.
I can achieve this using a temp table or using a loop, but I'm wondering if I can do it using just a select statement?

Answer 1

SELECT MIN(t1.ID+1) as 'MinID'
FROM table t1 LEFT JOIN table t2
On t1.ID+1=t2.ID
Where t2.OtherField IS NULL

Answer 2

select
min(nt.id)
from numbertable nt
left outer join originaldata od
on nt.id=od.id
where od.id is null
have a number table that goes from 1 to your max value (or higher)

Answer 3

SELECT DISTINCT x + 1 "val"
EXCEPT SELECT DISTINCT x "val"
ORDER BY "val" ASC
LIMIT 1
What about this?

Answer 4

SELECT Min(id)
FROM (SELECT 1 id
FROM tablea
WHERE 1 NOT IN (SELECT id
FROM tablea)
UNION
SELECT id + 1 id
FROM tablea
WHERE id + 1 NOT IN (SELECT id
FROM tablea)) AS min_ids;

Answer 5

try this:(Updated)
declare #dummy varchar(10) ;
set #dummy =(select top(1) id from dbo.b)
if( #dummy= '1')
begin
select top(1)l.id + 1 as start
from dbo.b as l
left outer join dbo.b as r on l.id + 1 = r.id
where r.id is null
end
else
begin
select '1'
end

Answer 6

Give this a try:
declare #TestTable table (
col int
)
/* Test Case 1: 1,2,9 */
insert into #TestTable
(col)
select 1 union all select 2 union all select 9
SELECT MinValue = (SELECT ISNULL(MAX(t2.col),0)+1
FROM #TestTable t2
WHERE t2.col < t1.col)
FROM #TestTable t1
WHERE t1.col - 1 NOT IN (SELECT col FROM #TestTable)
AND t1.col - 1 > 0
delete from #TestTable
/* Test Case 2: 9,10,11 */
insert into #TestTable
(col)
select 9 union all select 10 union all select 11
SELECT MinValue = (SELECT ISNULL(MAX(t2.col),0)+1
FROM #TestTable t2
WHERE t2.col < t1.col)
FROM #TestTable t1
WHERE t1.col - 1 NOT IN (SELECT col FROM #TestTable)
AND t1.col - 1 > 0

Answer 7

I duplicated my answer from here:
SELECT MIN(a.id) + 1 AS firstfree
FROM (SELECT id FROM table UNION SELECT 0) a
LEFT JOIN table b ON b.id = a.id + 1
WHERE b.id IS NULL
This handles all cases I can think of - including no existing records at all.
The only thing I don't like about this solution is that additional conditions have to be included twice, like that:
SELECT MIN(a.id) + 1 AS firstfree
FROM (SELECT id FROM table WHERE column = 4711 UNION SELECT 0) a
LEFT JOIN table b ON b.column = 4711 AND b.id = a.id + 1
WHERE b.id IS NULL
Please also notice the comments about locking and concurrency - the requirement to fill gaps is in most cases bad design and can cause problems. However, I had a good reason to do it: the IDs are to be printed and typed by humans and we don't want to have IDs with many digits after some time, while all the low ones are free...