CODEWITHSUNDEEP
sqldatabaseoracle-database
xMilos
xMilos

Reputation: 2018

Does getting less rows from database increase performance?

I have a simple question. Assume that the following sql returns over milion records:

Select * from Table

If I only need to work with 100 records, will limiting rows increase significantly the performance and why ?

Example oracle sql :

Select * from Table where rownum<=100

Upvotes: 0

Views: 105

Answers (2)

Gaurav Kumar Sinha
Gaurav Kumar Sinha

Reputation: 16

No . The best way to find an answer is quickly generate an Explain plan . And see the relative cost of execution . It will give you the quick view . Returning row is display part but fetching of the row done on the condition . So preferably it will not be slower and it attest what i am saying generate the explain plan it will give the clear picture

Upvotes: 0

Gordon Linoff
Gordon Linoff

Reputation: 1270483

If you are reading all the rows, then limiting the number of rows will be more efficient.

If you are reading the rows through -- say -- a cursor, then you probably will not see any difference in performance.

If your "table" is really a "view", then the two queries might optimize differently.

Upvotes: 3

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