CODEWITHSUNDEEP
sql
fen1ksss
fen1ksss

Reputation: 1120

different results in sql

I have two queries:

1)

SELECT a.n
FROM account a, contract c
WHERE c.n = a.r$contract
AND c.n IN (
    SELECT account.n
    FROM account, contract
    WHERE contract.n = account.r$contract
    AND account.n = contract.n )
ORDER BY a.n

and

2)

SELECT account.n
FROM account, contract
WHERE contract.n = account.r$contract
AND account.n = contract.n

In 1 there are 47 rows, but in 2 - 15. I can't understand why

Upvotes: 0

Views: 45

Answers (1)

FrancescoMM
FrancescoMM

Reputation: 2960

Not sure, I'll just try...

If query 2 returns 15 rows, then also the inner select of query 1 does, as it looks identical to me..

so query 1 is like

SELECT a.n
FROM account a, contract c
WHERE c.n = a.r$contract
AND c.n IN ( <any of the 15 values> )
ORDER BY a.n

And that is different from

SELECT a.n
FROM account a, contract c
WHERE c.n = a.r$contract
AND c.n = a.n              ( <-just one possible value)
ORDER BY a.n

So that might explain why you get different result sets.

Upvotes: 1

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