--查询用户下的表数量
SELECT COUNT(1) FROM USER_TABLES;

--查询用户下的表的字段数量
SELECT COUNT(1)
  FROM USER_COL_COMMENTS C
 WHERE EXISTS
 (SELECT 1 FROM USER_TABLES T WHERE T.TABLE_NAME = C.TABLE_NAME);
 
--查询表记录数量
SELECT T.TABLE_NAME,T.NUM_ROWS,T.BLOCKS,T.EMPTY_BLOCKS
  FROM USER_TABLES T;

--查询表备注
SELECT TABLE_NAME,TABLE_TYPE,COMMENTS
  FROM USER_TAB_COMMENTS
 WHERE COMMENTS LIKE '%字典%'


----查询表所占空间
analyze table T_DATA compute statistics;

SELECT NUM_ROWS,AVG_ROW_LEN
  FROM USER_TABLES
 WHERE TABLE_NAME = 'T_DATA';

SELECT SEGMENT_NAME,SUM(BYTES) / 1024 / 1024
  FROM USER_EXTENTS
 GROUP BY SEGMENT_NAME;