Query time question

Hello all,

    I am using TKPROF to find the elapsed time of queries. I have a SQL file that contains the following statements:

Q1 : select a,b,c,sum(d) d from main_tbl group by a,b,c;
Q2 : select a,sum(d) from from main_tbl group by a;
Q3 : select b,sum(d) from from main_tbl group by b;
Q4 : select c,sum(d) from from main_tbl group by c;

    The elapsed time are: (afting running this SQL file in SQL*Plus)

Q1 : 10s
Q2 : 1s
Q3 : 1s
Q4 : 1s

   Then I issue Q3 in SQL*Plus again. However, I find that the query time of running Q3 alone is 3s. I submit this query again in SQL*Plus and find that the query time is still 3s.

   Could anyone tell me why there is time differences between these two running? Is data stored in memory when running the SQL file? If yes, how can I clear all the data stored in memory before running a SQL statement?

Thanks,
Daivd

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Before you buy. Received on Sun Jan 23 2000 - 03:50:51 CST