bitwise comparison in bit columns - sql

Question

I have a database table with columns shaped as following:
| ID | name | A | B | C | D |
| 1 | foo | 1 | 0 | 0 | 1 |
| 2 | bar | 0 | 0 | 1 | 1 |
| 3 | foo | 1 | 1 | 0 | 0 |
| 4 | bar | 1 | 1 | 0 | 0 |
A, B, C and D are bit columns.
I need to get the name values of the rows of which there at least two and that both have at least one identical bit column set to true. the result set I want to get for the given example is as following:
| name |
| foo |
I can do the following:
SELECT l.name
FROM dummy l
INNER JOIN dummy r ON l.name = r.name
WHERE (l.A = 1 AND r.A = 1)
OR (l.B = 1 AND r.B = 1)
OR (l.C = 1 AND r.C = 1)
OR (l.D = 1 AND r.D = 1)
GROUP BY l.name
HAVING COUNT(*) > 1
But this gets unreadable soon since the table is massive. I was wondering if there was a bitwise solution to solve this

Answer 1

I suspect that your data model is wrong. It feels like A-D represent the same "type" of thing and so the data ought to be represented using a single column that contains the data values A-D and (if necessary) one column to store the 1 or 0, with separate rows for each A-D value. (But then, of course, we can use the presence of a row to indicate a 1 and the absence of the row to represent a 0).
We can use UNPIVOT to get this "better" structure for the data and then the query becomes trivial:
declare #t table (ID int not null, name char(3) not null, A bit not null, B bit not null,
C bit not null, D bit not null)
insert into #t(ID,name,A,B,C,D) values
(1,'foo',1,0,0,1),
(2,'bar',0,0,1,1),
(3,'foo',1,1,0,0),
(4,'bar',1,1,0,0)
;With ProperLayout as (
select ID,Name,Property,Value
from #t t
unpivot (Value for Property in (A,B,C,D)) u
where Value = 1
)
select name,Property
from ProperLayout
group by name,Property
having COUNT(*) > 1
Result:
name Property
---- ---------
foo A
(Note also that the top of my script is not much different in size to the sample data in your question but has the massive benefit that it's runnable)

Answer 2

In similar way you could also use Apply opertaor
SELECT a.name FROM table t
CROSS APPLY (
VALUES (name, 'A', A), (name, 'B', B), (name, 'C', C), (name, 'D', D)
)a(name , names , value)
WHERE a.value = 1
GROUP BY a.name, a.Names, a.value
HAVING COUNT(*) > 1

Answer 3

From your description, you seem to want:
SELECT l.name
FROM dummy l
GROUP BY l.name
HAVING SUM( CAST(A as int) ) >= 2 OR
SUM( CAST(B as int) ) >= 2 OR
SUM( CAST(C as int) ) >= 2 OR
SUM( CAST(D as int) ) >= 2 ;
This is based on the description. I don't know what the same result row has to do with the question.

Answer 4

It is not hard to read. It is just long.
This would be more efficient:
SELECT distinct l.name
FROM dummy l
INNER JOIN dummy r
ON l.name = r.name
and l.id < r.id
and ( (l.A = 1 AND r.A = 1)
OR (l.B = 1 AND r.B = 1)
OR (l.C = 1 AND r.C = 1)
OR (l.D = 1 AND r.D = 1)
)
order by l.name
You could build it up reading sys.columns
I don't think TSQL has any bitwise operators.