资料参考： https://www.cnblogs.com/nayitian/archive/2013/08/02/3231784.html
https://blog.csdn.net/yangzjchn/article/details/81019449
表内字段内容
select case when col.column_name = utc.column_name then '1' else '0' end isKey, utc.column_name name, utc.data_type type,ucc.comments remark from user_tab_columns utc, user_col_comments ucc，user_constraints con, user_cons_columns col where utc.table_name = ucc.table_name and utc.column_name = ucc.column_name and utc.table_name = col.table_name and con.constraint_name=col.constraint_name and con.constraint_type='P' and utc.table_name = '表名' order by column_id表内容
select t.table_name as name, c.comments as remark, o.created as createTime from user_tables t , USER_OBJECTS o, user_tab_comments c " where t.table_name = o.object_name and t.table_name = c.table_name 查询表基本信息 select utc.column_name,utc.data_type,utc.data_length,utc.data_precision, utc.data_Scale,utc.nullable,utc.data_default,ucc.comments from user_tab_columns utc,user_col_comments ucc where utc.table_name = ucc.table_name and utc.column_name = ucc.column_name and utc.table_name = 'BBSDETAIL' order by column_id;order by column_id的意义是使得结果按照设计数据结构时的顺序显示。
输出：
DETAIL_ID NUMBER 22 N 明细编号 TITLE VARCHAR2 100 N 标题 CATEGORY_ID NUMBER 22 N 分类编号（外键） DISTRICT_ID NUMBER 22 N 城市编号（外键） ADDRESS VARCHAR2 500 Y 地址
查询表主键 select col.column_name from user_constraints con,user_cons_columns col where con.constraint_name=col.constraint_name and con.constraint_type='P' and col.table_name='BBSDETAIL';输出：
DETAIL_ID
查询表外键 select distinct(ucc.column_name) column_name,rela.table_name,rela.column_name column_name1 from user_constraints uc,user_cons_columns ucc, (select t2.table_name,t2.column_name,t1.r_constraint_name from user_constraints t1,user_cons_columns t2 where t1.r_constraint_name=t2.constraint_name and t1.table_name='BBSDETAIL') rela where uc.constraint_name=ucc.constraint_name and uc.r_constraint_name=rela.r_constraint_name and uc.table_name='BBSDETAIL';输出：
CATEGORY_ID BBSCATEGORY CATEGORY_ID DISTRICT_ID BBSDISTRICT DISTRICT_ID
