1) Oracle也推荐应该在Oracle生成执成计划之前先Gather一下，以确保统计信息正确，这样生成的执行计划才尽量少走弯路。

--查看Table信息

  SELECT dt.table_name, dt.num_rows, dt.blocks, dt.empty_blocks AS empty
      ,dt.avg_space, dt.chain_cnt, dt.avg_row_len
      ,TO_CHAR (dt.last_analyzed, 'MM/DD/YYYY HH24:MI:SS')
  FROM dba_tables dt

  WHERE dt.owner = 'Module Name'

    AND dt.table_name = 'Table Name'

--另一种方式查看某Table信息

   SYS.DBMS_STATS.get_table_stats (ownname       => 'Module Name'
                                  ,tabname       => 'Table Name'
                                  ,partname      => NULL
                                  ,stattab       => NULL
                                  ,statid        => NULL
                                  ,numrows       => v_num_rows
                                  ,numblks       => v_num_blocks
                                  ,avgrlen       => v_avg_row_len
                                  ,statown       => NULL
                                  );

--Analyse一个Table

--gather一个schema

   SYS.DBMS_STATS.gather_schema_stats (ownname => 'Module Name');

2)Trace Oracle实际执行该SQL时所计算的数据、分析的路径以及消耗的Cost

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