CODEWITHSUNDEEP
sql
Rachit Agrawal
Rachit Agrawal

Reputation: 735

Alternative for exists query

I have the following query :

update tab1.abc,
tab1.sbd = (select tab2.abc, tab2.sbd from tab2,tab1 where --some conditions)
where exists(select tab2.abc, tab2.sbd from tab2,tab1 where --some conditions)

Now my task is to optmize this query.

I believe removing the exists clause or combining both the where clauses would help a lot. But how to do it ?

PS : exists clause is in place because I want the number of rows updated to be zero if the select clause returns zero rows.

Upvotes: 0

Views: 13574

Answers (2)

Lajja Thaker
Lajja Thaker

Reputation: 2041

you can use IN keyword 

update tab1.abc,
tab1.sbd = (select tab2.abc, tab2.sbd from tab2,tab1 where --some  conditions)
where something in 
(select tab2.abc, tab2.sbd from tab2,tab1 where --some conditions)

refer below links:

IN (TSql)

SQL IN

Upvotes: 0

Mahmoud Gamal
Mahmoud Gamal

Reputation: 79889

JOIN the two tables instead of EXISTS. Something like the following:

UPDATE tab1
INNER JOIN tab2 ON --some join condition
SET sbd = --something
AND abc = --other something
WHERE --some conditions

Upvotes: 2

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