Can I get duplicate results (from one table) in an INTERSECT operation between two tables? - sql

Question

I know the wording of the question is awkward, but I couldn't phrase it any better. Let me explain the situation.
There's table A which has a bunch of columns (a, b, c ... ) and I run a SELECT query on it like so:
SELECT a FROM A WHERE b IN ('....') (the ellipsis indicates a number of values to be matched to)
There's another table B which has a bunch of columns (d, e, f ... ) and I run a SELECT query on it like so:
SELECT d FROM B WHERE f = '...' (the ellipsis indicates a single value to be matched to)
Now I should say here that the two tables store different types of information about the same entity, but the columns a and d contain the exact same data (in this case, an ID). I want to find out the intersection of the two tables so I run this:
SELECT a FROM A WHERE b IN ('....') INTERSECT SELECT d FROM B WHERE f = '...'
Now here's the problem:
The first SELECT contains a set of values in the WHERE clause, right? So let's say the set is (1234, 2345,3456). Now, the result of this query when b is matched ONLY to 1234 is, let's say, abc. When it's matched to 2345, it's def, suppose. And matching to 3456, it gives abc.
Let's suppose these two results (abc and def) are also in the set of results from the second SELECT.
So, now, putting back the entire set of values to matched into the WHERE clause, the INTERSECT operation will give me abc and def. But I want abc twice since two values in the WHERE clause set match to the second SELECT.
Is there any way I can get that?
I hope it's not too complicated to understand my problem. This is a real-life problem I'm facing in my job.
Data structure and my code
Table A contains general information about a company:
company_id | branch_id | no_of_employees | city
Table B contains the financials of the company:
company_id | branch_id | revenue | profits
First SELECT:
SELECT branch_id FROM A WHERE CITY IN ('Dallas', 'Miami', 'New Orleans')
Now, running each city separately in the first SELECT, I get the branch_ids:
branch_id | city
23 | Dallas
45 | Miami
45 | New Orleans
Once again, this seems impractical as to how two cities can have the same branch ids, but please bear with me on this.
Second SELECT:
SELECT branch_id FROM B
WHERE REVENUE = 5000000
I know this is a little impractical, but for the purpose of this example, it suffices.
Running this query I get the following set:
11
23
45
22
10
So the INTERSECT will give me just 23 and 45. But I want 45 twice, since both Miami and New Orleans have that branch_id and that branch_id has generated a revenue of 5 million.

Answer 1

Directly from Microsoft's documentation (https://msdn.microsoft.com/en-us/library/ms188055.aspx)
:
"INTERSECT returns distinct rows that are output by both the left and right input queries operator."
So NO, it is not possible to get the same value twice when using INTERSECT because the results will be DISTINCT. However if you build an INNER JOIN correctly you can do essentially the same thing as INTERSECT except keep the repetitive results by NOT using distinct or group by.
SELECT
A.a
FROM
A
INNER JOIN B
ON A.a = B.d
AND B.F = '....'
WHERE b IN ('....')
And for your specific Example that you edited:
SELECT
branch_id
FROM
A
INNER JOIN B
ON A.branch_id = B.branch_id
AND B.REVENUE = 5000000
WHERE A.CITY IN ('Dallas', 'Miami', 'New Orleans')

Answer 2

You overcomplicated your task a lot:
SELECT *
FROM A
WHERE CITY IN (...)
AND EXISTS
(
SELECT 1 FROM B
WHERE B.REVENUE = 5000000
AND B.branch_id = A.branch_id
)
INTERSECT and EXCEPT are both returning row sets with DISTINCT applied.
Regular joining/filtering operations are not performed by INTERSECT or EXCEPT.