How can I use SUM for bit columns?

Question

How can use the function SUM() for bit columns in T-SQL?

When I try do it as below:

SELECT SUM(bitColumn) FROM MyTable;

I get the error:

Operand data type bit is invalid for sum operator.

Answer 1

SELECT SUM(CAST(bitColumn AS INT))
FROM dbo.MyTable

need to cast into number

or another solution -

SELECT COUNT(*)
FROM dbo.MyTable
WHERE bitColumn = 1

Answer 2

You could consider 0 as nulls and simply count the remaining values:

SELECT count(nullif(bitColumn, 0))
FROM MyTable;

Answer 3

You can achieve by using CONVERT,

SELECT SUM(CONVERT(INT, bitColumn)) FROM MyTable

Answer 4

SELECT SUM(bitColumn * 1) FROM dbo.MyTable

Converts the bit into int, by multiplication, clean and simple

Answer 5

You can use CAST and CONVERT function for data type to integer or number data type.

Try this code blocks :

SELECT SUM(CAST(bitColumn AS INT)) as bitColumn
FROM MyTable

or

SELECT CONVERT(INT, bitColumn) 
FROM MyTable

Answer 6

You could use SIGN function:

CREATE TABLE tab_x(b BIT);
INSERT INTO tab_x(b) VALUES(1),(0),(0),(NULL),(0),(1);

SELECT SUM(SIGN(b))
FROM tab_x;
-- 2

DBFiddle Demo

Answer 7

Somewhat cryptically:

declare @Foo as Bit = 1;
-- @Foo is a Bit.
select SQL_Variant_Property( @Foo, 'BaseType' );
-- But adding zero results in an expression with data type Int.
select SQL_Variant_Property( @Foo + 0, 'BaseType' );
select Sum( @Foo + 0 );

declare @Samples as Table ( Foo Bit );
insert into @Samples ( Foo ) values ( 0 ), ( 1 ), ( 0 ), ( 0 ), ( 1 ), ( 1 ), ( 1 ), ( 1 );
select Sum( Foo + 0 ) from @Samples;

This certainly doesn't improve readability or maintainability, but it is compact.