Question

I have a table with int values being used as bitfields (where each bit is a flag).

Now I would like to aggregate them with a binary operation (in my case OR) so that:

SELECT 1 AS bitfield
INTO #TABLE
UNION ALL SELECT 1 + 2 + 8 + 32
UNION ALL SELECT 2 + 128
UNION ALL SELECT 2 + 32

SELECT AND_AGGR(bitfield) -- Invalid because AND_AGGR doesn't exist
FROM #TABLE

DROP #TABLE

would result in the value 171

What would be a good way to do this that hopefully doesn’t require a lot of | and MAX (but if you must, you must)?

I am using MS SQL Server 2008 myself, but solutions on other servers are also of interest.

Answer 1

If you’re expecting the result 171, surely you mean binary OR not AND?

In any case, this solution aggregates the values into a variable:

SELECT 1 AS bitfield
INTO #TABLE
UNION ALL SELECT 1 + 2 + 8 + 32
UNION ALL SELECT 2 + 128
UNION ALL SELECT 2 + 32

DECLARE @i int = 0

SELECT @i = @i | bitfield
FROM #TABLE

SELECT @i

DROP TABLE  #table

This might not meet your requirements if you want to group the aggregation by another field.

It is also unlikely to perform well on a large table.