CODEWITHSUNDEEP
sqloracle-database
user1663715
user1663715

Reputation: 396

Performance difference in two SQL queries

This is simplified version of two views:

viewA is select * from myTable;
viewB is select * from viewA;

Is there any performance difference between selecting from viewA directly and selecting from viewB because selecting from viewB has another layer which is viewA?

Upvotes: 2

Views: 113

Answers (1)

wittrup
wittrup

Reputation: 1565

CREATE OR REPLACE FORCE VIEW  "VIEWA" ("TITLE", "VALUE1", "VALUE2", "ID") AS 
  select "TITLE","VALUE1","VALUE2","ID" from dati
/
​CREATE OR REPLACE FORCE VIEW  "VIEWB" ("TITLE", "VALUE1", "VALUE2", "ID") AS 
  select "TITLE","VALUE1","VALUE2","ID" from viewa
/

​Explain plan for select * from viewA

Operation           Options         Object  Rows    Time    Cost    Bytes   Filter          Access
                                                                            Predicates *    Predicates
SELECT STATEMENT                            4       1       3       268      
TABLE ACCESS        STORAGE FULL    DATI    4       1       3       268

Explain plan for select * from viewB

Operation           Options         Object  Rows    Time    Cost    Bytes   Filter          Access
                                                                            Predicates *    Predicates
SELECT STATEMENT                            4       1       3       268      
TABLE ACCESS        STORAGE FULL    DATI    4       1       3       268

My answer would have to be: no, there is not any performance difference.

Upvotes: 3

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