--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;