Re: Need help Regarding executing select query
Lew wrote:
Pradeep wrote:
I have one problem in getting Results using select Query...
Query:
------------ -
Select product_sys_ id,product_ name from Product where product_sys_
id in(9,6,4,1,2) ;
Result:(Actual)
------------ --------- --------- ----
product_sys_ id product_name
------------ --------- --------- --------- -----
1 PR1
2 PR9
4 PR5
6 PR787
9 PR657
Observe that in the Result product_sys_ ids are getting in the sorted
order not in the order specified in the Select Query...
I want to get the Result of product_sys_ ids in the order specified
in the select
Query....i.e. ,
Result:(Expected)
------------ --------- ------
product_sys_ id product_name
------------ --------- --------- --------- -----
9 PR657
6 PR787
4 PR5
1 PR1
2 PR9
Can anybody know the solution ???
Use an ORDER BY clause in your SELECT.
To expand on that - SELECT is not guaranteed to return any particular order
absent an ORDER BY clause.
You don't say how you get the more "random"-seeming results. Was it via a
command line SQL tool, such as psql?
That tool in turn communicates with the RDBMS engine, as the JDBC driver must.
That tool, like your JDBC calls, is a black box to the programmer / user.
We don't get to know, much less influence, how the RDBMS receives the SELECT
or how it plans it, save that it must conform to SQL semantics. SQL semantics
explicitly disclaim order for the results.
Ergo, if you do not ORDER BY your query, you have to take it in any order that
it has. Any system or technique that guarantees the order of the SELECT any
other way will be non-compliant.
That said, we do not know that the RDBMS-to-JDBC link is re-ordering your
results. Perhaps the result set is arriving at the JVM in one order, and at
your ResultSet (or RowSet) in a different order. If so, there are two
possible reasons:
1) The JDBC mechanism likes to arbitrarily re-order results. This is
extremely unlikely, since in the general case there is no need to do this and
it would slow performance. Java authors and API writers are already sensitive
to accusations that Java is slow; they're unlikely to bog JDBC down without
any benefit.
2) Your application is ordering the result set. This could be true, and if so
that is good news, because it means that you can fix it.
Can you tell whether the RDBMS is ordering the results in this unexpected way,
or if it's happening in your program or the JDBC layer?
--
Lew