Rats... itchy fingers on the send button...
On Jun 11, 2005, at 12:32 PM, Puneet Kishor wrote:
tbl1(a INTEGER PRIMARY KEY, b VARCHAR(200) UNIQUE) with 200k+ records
tbl2(a INTEGER PRIMARY KEY, b VARCHAR(200) UNIQUE) with a few k records
values in col(b) in tbl1 are not common with the values in col(b) in
tbl2
I want to find a given string in either tbl1 or tbl2. Which of the
following is better?
SELECT *
FROM ((SELECT * FROM tbl1) UNION (SELECT * FROM tbl2))
WHERE b = 'foo'
or
SELECT * FROM tbl1 WHERE b = 'foo'
UNION
SELECT * FROM tbl1 WHERE b = 'foo'
In my experience, the first SELECT is much slower, but are there any
gotchas with the second SELECT? Is there a better way?
My question stems from my understanding that I can convert the first
SELECT into a VIEW and then conveniently SELECT against that VIEW.
CREATE VIEW bigview AS (
SELECT * FROM ((SELECT * FROM tbl1) UNION (SELECT * FROM tbl2))
)
SELECT * FROM bigview WHERE b = 'foo'
But, that will be slow, no?
--
Puneet Kishor
