字段注释

select   *   from   user_col_comments;

表注释

select   *   from   user_tab_comments;

//

查询字段类型

select column_name,data_type,data_length from user_tab_columns where table_name='TableName' and column_name in ('AGE_ID','MONTH_ID') 

Column_name值为大写

//

查询表的主键

select * from user_cons_columns where table_name='D_DAY'

//

select column_name from user_cons_columns where constraint_name in (select constraint_name from user_constraints where table_name = 'D_DAY' and constraint_type = 'P')

//查询某表字段的主键名称及类型

select column_name,data_type,data_length,DATA_PRECISION||','||DATA_SCALE from user_tab_columns v  join  (select column_name from user_cons_columns where constraint_name in (select constraint_name from user_constraints where table_name = 'D_DAY' and constraint_type = 'P')) t using (column_name) where table_name='D_DAY'