创建表，创建索引，添加数据，此时表跟索引的统计信息都没有。

12:40:18 rodman@RODMAN>create table t as select object_id,object_name from dba_objects where 1=0;


Table created.


12:40:47 rodman@RODMAN>create index index_t on t(object_id);


Index created.


12:40:56 rodman@RODMAN>insert into t select object_id,object_name from dba_objects;


80784 rows created.


12:41:06 rodman@RODMAN>select num_rows,avg_row_len,blocks,last_analyzed from user_tables where table_name='T';


  NUM_ROWS AVG_ROW_LEN     BLOCKS LAST_ANALYZED
---------- ----------- ---------- -------------------




12:41:13 rodman@RODMAN>select blevel,leaf_blocks,distinct_keys,last_analyzed from user_indexes where table_name='T';


    BLEVEL LEAF_BLOCKS DISTINCT_KEYS LAST_ANALYZED
---------- ----------- ------------- -------------------
         0           0             0 2016-03-21 12:40:55

执行表的统计信息收集，并且连带索引信息也收集完成。

12:43:25 rodman@RODMAN>exec dbms_stats.gather_table_stats('RODMAN','T');


PL/SQL procedure successfully completed.


12:43:59 rodman@RODMAN>
12:44:00 rodman@RODMAN>select num_rows,avg_row_len,blocks,last_analyzed from user_tables where table_name='T';


  NUM_ROWS AVG_ROW_LEN     BLOCKS LAST_ANALYZED
---------- ----------- ---------- -------------------
     80784          30        496 2016-03-21 12:43:58


12:44:06 rodman@RODMAN>select blevel,leaf_blocks,distinct_keys,last_analyzed from user_indexes where table_name='T';


    BLEVEL LEAF_BLOCKS DISTINCT_KEYS LAST_ANALYZED
---------- ----------- ------------- -------------------
         1         167         80784 2016-03-21 12:43:59


或者用：
analyze table t compute statistics;
analyze table t compute statistics for all indexes;









用户级别
$ sqlplus / as sysdba
Sql> BEGIN
  SYS.DBMS_STATS.GATHER_SCHEMA_STATS (
      OwnName        => 'ADMIN'
    ,Estimate_Percent  => SYS.DBMS_STATS.AUTO_SAMPLE_SIZE
    ,Degree            => 4
    ,Cascade           => TRUE
    ,No_Invalidate     => TRUE);
END;
/

数据库级别
$ sqlplus / as sysdba
Sql> BEGIN
  SYS.DBMS_STATS.GATHER_DATABASE_STATS (
    Estimate_Percent  => SYS.DBMS_STATS.AUTO_SAMPLE_SIZE
    ,Degree            => 4
    ,Cascade           => TRUE
    ,No_Invalidate     => TRUE);
END;
/