[bbk2340] 第45集 - Chapter 09-Optimizing Sore Perations(00)
Ojbectives
After completing this lesson,you should be able to do the following
Understanding Statistics
管理statistic的package:dbms_stats.
Managing Statistics
Use the dbms_stats packages:
- gather_table_stats
- gather_index_stats
- gather_schema_stats
- gahter_database_stats
- gather_stable_stats
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
SQL> create table t(id int,name char(10)); Table created. SQL> insert into t values(0,'arcerzhang'); 1 row created. SQL> insert into t values(1,'arcerzhang'); 1 row created. SQL> insert into t values(2,'arcerzhang'); 1 row created. SQL> commit; Commit complete. SQL> select * from t; ID NAME ---------- ---------- 0 arcerzhang 1 arcerzhang 2 arcerzhang
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
SQL> select num_rows,blocks from dba_tables where owner='HR' and table_name='T'; NUM_ROWS BLOCKS ---------- ----------
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
SQL> exec dbms_stats.gather_table_stats('HR','T'); PL/SQL procedure successfully completed.
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
SQL> select num_rows,blocks from dba_tables where owner='HR' and table_name='T'; NUM_ROWS BLOCKS ---------- ---------- 3 5
分析完成后,将分析结果存放在数据字典里面的;上述图表列出了Tables、Columns、Indexes对应的信息(分析完成数据之后,各自存放在数据字典表中的位置).
注意:上述信息,是10g以后才有的,之前的版本是没有这些数据的.
When to Gather Statistics