SQL query with "parameters"

Question

Hi,
I want a sql query as follows (but it seems not be as simple as that...)
select A1, A2,
select sum(B3)
from B1 = A2
where
from A
where A1 = '1001'
is it possible, in some way, to have A2 from outer select statement as a parameter to inner select statement?

Answer 1

Hi,
user8819407 wrote:
Hi,
I want a sql query as follows (but it seems not be as simple as that...)
select A1, A2,
select sum(B3)
from B1 = A2
where
from A
where A1 = '1001'
is it possible, in some way, to have A2 from outer select statement as a parameter to inner select statement?Yes, you can reference columns from a parent query within its child query.
For example:
select  A1, A2,
         select  sum (b.B3)
         from   b
         where  b.B1 = a.A2
from     A
where     A1 = '1001'
;Within the sub-query, you don't have to qualify columns from b; that is, b3 is assumed to mean b.b3. If the column name is unique, you don't have to qualify columns from table a, either. That is, if b does not have a column called a2, then a2 in the sub-query could only mean a.a2, and Oracle doesn't make you spell out which table a2 comes from, but it makes the code a lot easier to understand and debug if you do qualify the columns.
By the way, a sub-query that references its parent query like this is called a Correlated Sub-Query .
"Parameter" doesn't really apply to this situation.