Another stupid question :)

Good time of the day!

There are three tables:

CREATE big (
id     int4 PRIMARY KEY,
ref1   int4,
ref2   int4,
...
);

CREATE ref1 (
id     int4  PRIMARY KEY,
...
);

CREATE ref2 (
id     int4 PRIMARY KEY,
...
);

Tables ref1 and ref2 are small, like 10-15 records. Table big is
large. Often I need to get data from all tables. Which way is better
in terms on performance:

SELECT big.*, ref1.*, ref2.* FROM big, ref1, ref2 WHERE big.ref1 =
ref1.id AND big.ref2 = ref2.id AND ...

OR make 3 separate queries like, say
SELECT * FROM big WHERE ...
and then in the loop select corresponding data from small tables?


And more general question: how queries affect performance? Which way
is better: run two queries which will return, say, 5 records each, or
run one query which will return, say, 20 records and then drop
unneeded records in my backend application?




Best regards,
 Dmitri ( mailto:dmitri@listsoft.ru )

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