The following factors play a role during the processing of an SQL statement:
· Type of physical storage of a table
· Size of the tables (Number of rows and B* tree pages)
· Definition of the table (especially the key columns)
· Definition of indexes
· Type of SQL statement (SELECT, INSERT, UPDATE, DELETE)
· Elements of a SELECT statement (ORDER clause, UPDATE clause, DISTINCT specification, and specification of FOR REUSE)
· Changes that are specified in the UPDATE statement
These factors especially influence the processing of an SQL statement if the SQL statement triggers a search of a large quantity of data. This generally happens with the following SQL statements:
SELECT ...
INSERT ...
SELECT ...
UPDATE ...
WHERE <search_condition>
DELETE ...
WHERE <search_condition>