Обсуждение: Which Join is better

Dear all,

Just want to know which join is better for querying data faster.

I have 2 tables A ( 70 GB ) & B ( 7 MB )

A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.

select p.* from table A p, B q where p.id=q.id

or

select p.* from table B q , A p where q.id=p.id


Thanks

El Martes 02 Agosto 2011, Adarsh Sharma escribió:
> Dear all,
>
> Just want to know which join is better for querying data faster.
>
> I have 2 tables A ( 70 GB ) & B ( 7 MB )
>
> A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.
>
> select p.* from table A p, B q where p.id=q.id
>
> or
>
> select p.* from table B q , A p where q.id=p.id
>
>
> Thanks


Hi Adarsh,

What does a "EXPLAIN ANALYZE" say after a VACCUM?

--
María Arias de Reyna Domínguez
Área de Operaciones

Emergya Consultoría
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www.emergya.es

Unless you use the explicit join syntax:


select p.* from A p join B q on (p.id = q.id)

and also set  join_collapse_limit= 1
The order of the joins is determined by the planner.


Also explain is your friend :)

________________________________
From: Adarsh Sharma <adarsh.sharma@orkash.com>
To: pgsql-performance@postgresql.org
Sent: Monday, August 1, 2011 11:42 PM
Subject: [PERFORM] Which Join is better

Dear all,

Just want to know which join is better for querying data faster.

I have 2 tables A ( 70 GB ) & B ( 7 MB )

A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.

select p.* from table A p, B q where p.id=q.id

or

select p.* from table B q , A p where q.id=p.id


Thanks

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