is it possible to select EXISTS directly as a bit?
SqlSql ServerTsqlSql Problem Overview
I was wondering if it's possible to do something like this (which doesn't work):
select cast( (exists(select * from theTable where theColumn like 'theValue%') as bit)
Seems like it should be doable, but lots of things that should work in SQL don't ;) I've seen workarounds for this (SELECT 1 where... Exists...) but it seems like I should be able to just cast the result of the exists function as a bit and be done with it.
Sql Solutions
Solution 1 - Sql
No, you'll have to use a workaround.
If you must return a conditional bit 0/1 another way is to:
SELECT CAST(
CASE WHEN EXISTS(SELECT * FROM theTable where theColumn like 'theValue%') THEN 1
ELSE 0
END
AS BIT)
Or without the cast:
SELECT
CASE
WHEN EXISTS( SELECT 1 FROM theTable WHERE theColumn LIKE 'theValue%' )
THEN 1
ELSE 0
END
Solution 2 - Sql
SELECT CAST(COUNT(*) AS bit) FROM MyTable WHERE theColumn like 'theValue%'
When you cast to bit
- 0 -> 0
- everything else -> 1
- And NULL -> NULL of course, but you can't get NULL with COUNT(*) without a GROUP BY
bit
maps directly to boolean
in .net datatypes, even if it isn't really...
This looks similar but gives no row (not zero) if no matches, so it's not the same
SELECT TOP 1 CAST(NumberKeyCOlumn AS bit) FROM MyTable WHERE theColumn like 'theValue%'
Solution 3 - Sql
I'm a bit late on the uptake for this; just stumbled across the post. However here's a solution which is more efficient & neat than the selected answer, but should give the same functionality:
declare @t table (name nvarchar(16))
declare @b bit
insert @t select N'Simon Byorg' union select N'Roe Bott'
select @b = isnull((select top 1 1 from @t where name = N'Simon Byorg'),0)
select @b whenTrue
select @b = isnull((select top 1 1 from @t where name = N'Anne Droid'),0)
select @b whenFalse
Solution 4 - Sql
You can use IIF
and CAST
SELECT CAST(IIF(EXISTS(SELECT * FROM theTable
where theColumn like 'theValue%'), 1, 0) AS BIT)
Solution 5 - Sql
You can also do the following:
SELECT DISTINCT 1
FROM theTable
WHERE theColumn LIKE 'theValue%'
If there are no values starting with 'theValue' this will return null (no records) rather than a bit 0 though
Solution 6 - Sql
No it isn't possible. The bit data type is not a boolean data type. It is an integer data type that can be 0,1, or NULL.
Solution 7 - Sql
SELECT IIF(EXISTS(SELECT * FROM theTable WHERE theColumn LIKE 'theValue%'), 1, 0)
Solution 8 - Sql
Another solution is to use ISNULL
in tandem with SELECT TOP 1 1
:
SELECT ISNULL((SELECT TOP 1 1 FROM theTable where theColumn like 'theValue%'), 0)
Solution 9 - Sql
I believe exists can only be used in a where clause, so you'll have to do a workaround (or a subquery with exists as the where clause). I don't know if that counts as a workaround.
What about this:
create table table1 (col1 int null)
go
select 'no items',CONVERT(bit, (select COUNT(*) from table1) ) -- returns 'no items', 0
go
insert into table1 (col1) values (1)
go
select '1 item',CONVERT(bit, (select COUNT(*) from table1) ) --returns '1 item', 1
go
insert into table1 (col1) values (2)
go
select '2 items',CONVERT(bit, (select COUNT(*) from table1) ) --returns '2 items', 1
go
insert into table1 (col1) values (3)
go
drop table table1
go