Why the query returns more than one result?

Question

I have four SQL Server database tables:

1. inventory
2. inventory2
3. bdo
4. details

Structure is as:

inventory

AllocationID   MSISDN
1              3018440225
2              3028431115

Inventory2

    AllocationID   MSISDN
    1              3011234567
    2              3026440657
    3              3454159650

BDO

BDO_ID      BDO_MSISDN
1           3457076952
2           3005000475

Details

AllocationID    MSISDN
3               3454159650

Now I need to get the records from following query:

select a.msisdn, b.bdo_id
from details a, bdo b, inventory c, inventory2 d
where 
    a.msisdn = 3454159650
    and (a.allocationid = c.allocationid) or (a.allocationid = d.allocationid)
    and (c.bdo_id = b.bdo_id) or (d.bdo_id = b.bdo_id)

This query returns more than 1 result (all exactly same) why is it so??? if I am wrong please correct my concepts and query.

Answer 1

You have a very strange form for the query. First, you should use join syntax. Second, you seem to want a union between the two inventory tables:

select d.msisdn, b.bdo_id
from (select i.*
      from (select i.* from inventory i union all
            select i2.* from inventory i2
           ) i
     ) i join
     details d
     on d.allocationid = i.allocationid join
     bdo b
     on i.bdo_id=b.bdo_id
where d.msisdn = 3454159650;

Structuring the query as explicit joins should make it more efficient and should make it easier to understand, get correct, and maintain.

EDIT:

It is possible that you are missing some records in some tables. Try using this version with a left outer join :

select d.msisdn, b.bdo_id
from details d left outer join
     (select i.*
      from (select i.* from inventory i union all
            select i2.* from inventory i2
           ) i
     ) i
     details d
     on d.allocationid = i.allocationid left outer join
     bdo b
     on i.bdo_id=b.bdo_id
where d.msisdn = 3454159650;

Answer 2

I'm surprised it returns anything. You're referring to a bdo_id field that doesn't exist.

Your main problem is the priority of and over or

Try this instead

select a.msisdn,b.bdo_id
from details a,bdo b,inventory c,inventory2 d
where 
a.msisdn=3454159650
and ((a.allocationid = c.allocationid) or (a.allocationid = d.allocationid))
and ((c.bdo_id=b.bdo_id) or (d.bdo_id=b.bdo_id))

Answer 3

Your query does not return value. This query raise error. Last row of your query this

and (c.bdo_id = b.bdo_id) or (d.bdo_id = b.bdo_id)

C is your inventory table and inventory table has no column name with bdo_id

and

D is your inventory2 table and inventory2 table has no column name with bdo_id