Database table Analyze

Question

<p>
{color:#339966}Hi,
I have a very basic question.
I want to know what exactly happens in the Database architecture when a table analyze is done by gathering the stats.
How does this analyze helps in performance of queries.
Thanks
Mns{color}
</p>

Answer 1

hi,
Table analyze is done to get the internal details for the table like exact space used,exact blocks used,row chaining etc.
optimizer uses these details in creating execution plan for the statements for that table.
SQL> set lines 10000
SQL> select table_name,num_rows,blocks,chain_cnt,avg_row_len from user_tables where table_name='EMP';
TABLE_NAME NUM_ROWS BLOCKS CHAIN_CNT AVG_ROW_LEN
EMP
SQL> analyze table emp compute statistics;
Table analyzed.
SQL> select table_name,num_rows,blocks,chain_cnt,avg_row_len from user_tables where table_name='EMP';
TABLE_NAME NUM_ROWS BLOCKS CHAIN_CNT AVG_ROW_LEN
EMP 14 1 0 40
Regards
Edited by: NKU on Nov 5, 2008 12:28 AM