SQL query optimization

Hi!

I have some questions related with SQL query optimization (Oracle 10g Release 2).

It's like this:

Query A:
SELECT X."COL1", Y."COL8"
FROM "TBL1" X INNER JOIN "TBL2" Y ON (X."ID" = Y."XID") WHERE X."COL4" = 'xpto';

Query B:
select x.col1, y.col8
from tbl1 x, tbl2 y
where x.id = y.xid and x.col4 = 'xpto';


I usually code queries like "Query B", but recently a software tester told me that I should code like "Query A" and told me this:

1 - you should always use upper case.
2 - you should put quotes in column and table names
3 - you should use the JOIN syntax because it's the recommended syntax (ISSO/IEC 9075 SQL:2003)

And he justifies this with performance improvements.

And my questions are:

A) Does this make any sense?
B) Is the JOIN syntax better than the Oracle syntax (+) in terms of performance? Does it make any difference?
C) Does the upper case and quotes make any improvements?
D) Does any of this influences SQL statement processing phases?


Thanks

You can easily test it.
Run/trace both versions of the query and post results.

>>but recently a software tester told me that I should code like "Query A"

A tester will no doubt find query A more 'readable'

>>you should always use upper case.

ALWAYS? FOR EVERYTHING? personally I like upper case only on RESERVED words.

>>you should put quotes in column and table names

Personal preference. It's up to you.

>>you should use the JOIN syntax because it's the recommended syntax (ISSO/IEC 9075 SQL:2003)

If it's part of that ISO standard, and you want to meet that standard, then you probably should use it.

>>And he justifies this with performance improvements.

I'd ask for proof.
As PAVB suggests, how about some numbers to back it up?

>>A) Does this make any sense?

The questions make sense.

>>B) Is the JOIN syntax better than the Oracle syntax (+) in terms of performance? Does it make any difference?

No. To readability, yes. To the ISO, probably

>>C) Does the upper case and quotes make any improvements?

No. To readability, yes for the case; for me No for the quotes.

>>D) Does any of this influences SQL statement processing phases?

Unlikely.