subselects - which is faster? - Mailing list pgsql-sql

It's been a while since I've done much SQL.. 

. I'm wondering which of these two queries is faster (both get the
same result)?

. Which one is more correct?  Does it even matter or are they the
same?  The first one reads easier to me.

. What's the difference between "InitPlan" and "SubPlan"?

explain SELECT eqid,  (select name from tbleqattrtypes where id=     (select eqattrtypeid from tbleqattrs     where
id=main.eqattrid))asattrtype, eqattrid from tbleqattrmap as main;
 

NOTICE:  QUERY PLAN:
Seq Scan on tbleqattrmap main  (cost=0.00..1.15 rows=15 width=8) SubPlan   ->  Seq Scan on tbleqattrtypes
(cost=0.00..1.04rows=1 width=12)         InitPlan           ->  Seq Scan on tbleqattrs  (cost=0.00..1.09 rows=1
width=4)


explain SELECT eqid,   (select      (select name from tbleqattrtypes where id=sec.eqattrtypeid)   from tbleqattrs as
secwhere id=main.eqattrid)as attrtype, eqattrid from tbleqattrmap as main;                                   
 

NOTICE:  QUERY PLAN:
Seq Scan on tbleqattrmap main  (cost=0.00..1.15 rows=15 width=8) SubPlan   ->  Seq Scan on tbleqattrs sec
(cost=0.00..1.09rows=1 width=4)         SubPlan           ->  Seq Scan on tbleqattrtypes  (cost=0.00..1.04 rows=1
width=12)

One additional detail:  right now the tables are all very small, and
tbleqattrtypes will not grow much, but tbleqattrs will eventually be
very large.

Thanks, and sorry for bothering you all..
- Cedar