Info about "with" statement..

Question

Hi everybody,
I have seen too many threads using with statements in sql...
The general syntax is :
SQL> with t as
( select ...... from .....
union
select ...... from .....
)...... 'test' from t;
What is this and where can I found info about this......????
I use Ora 10g.
Thanks ,
Simon

Answer 1

Or, to put it in basic terms.....
When you want to test something and you need a sample set of data to use, rather than create a table and populate it with a whole load of inserts (or insert select) you can just specify a "With <name> as select...." clause before your query. This also means that you don't have to drop the table again when you're done testing.
Long winded way...
create table t as (select 1 id from dual union select 2 from dual union select 3 from dual);
select * from t;
drop table t;Simple way...
with t as (select 1 id from dual union select 2 from dual union select 3 from dual)
select * from t;The sample data is only in existence for the duration of the query, and it saves all of us here on the forums who answer peoples questions from creating loads of tables on our databases temporarily.
;)