select a.column_id as 列号, a.column_name as 列名, a.data_type as 类型,
decode(a.data_type,'NUMBER',a.data_precision,a.data_length) as 长度, a.data_scale as 小数位,
decode(e.uniqueness,'UNIQUE','Y','N') as 是否是唯一的, decode(e.key,'Y','Y','N') 是否是主键,
f.comments as 注释, a.nullable as 是否允许空, a.data_default as 默认值
from user_tab_columns a, user_col_comments f,
(select b.table_name, b.index_name,b.uniqueness, c.column_name,
decode(d.constraint_name,NULL,'N','Y') key
from user_indexes b, user_ind_columns c,
( select constraint_name from user_constraints where constraint_type='P' ) d
where b.index_name=c.index_name and b.index_name=d.constraint_name(+) ) e
where a.table_name='TEMPTABLE' and a.table_name=e.table_name(+) and a.column_name=e.column_name(+)
and a.table_name=f.table_name and a.column_name=f.column_name
order by a.column_id
select TC.table_name , TC.column_name ,TC.DATA_TYPE,TC.data_length,TC.data_precision,TC.nullable,
TC.char_col_decl_length,
decode(C.constraint_type,'P','PK','U','Unique','R','FK','C','Check',C.constraint_type)
from USER_TAB_COLUMNS TC,USER_CONS_COLUMNS CC ,user_constraints C
where TC.table_name = 'EMP'
and TC.table_name = CC.table_name(+)
and TC.column_name = CC.column_name (+)
and CC.constraint_name = C.constraint_name(+)
select A.column_name 字段名,A.data_type 数据类型,A.data_length 长度,A.data_precision
整数位, A.Data_Scale 小数位,A.nullable 允许空值,A.Data_default 缺省值,B.comments
备 注 from user_tab_columns A,user_col_comments B where a.COLUMN_NAME=b.column_name and A.Table_Name = B.Table_Name and A.Table_Name='TEST'
select table_name from user_tables; //当前用户的表
select table_name from all_tables; //所有用户的表
select table_name from dba_tables; //包括系统表
select table_name from dba_tables where owner='用户名'
user_tables：
table_name,tablespace_name,last_analyzed等
dba_tables：
ower,table_name,tablespace_name,last_analyzed等
all_tables：
ower,table_name,tablespace_name,last_analyzed等
all_objects：
ower,object_name,subobject_name,object_id,created,last_ddl_time,timestamp,status等
获取表字段：
select * from user_tab_columns where Table_Name='用户表';
select * from all_tab_columns where Table_Name='用户表';
select * from dba_tab_columns where Table_Name='用户表';
user_tab_columns：
table_name,column_name,data_type,data_length,data_precision,data_scale,nullable,column_id等
all_tab_columns ：
ower,table_name,column_name,data_type,data_length,data_precision,data_scale,nullable,column_id等
dba_tab_columns：
ower,table_name,column_name,data_type,data_length,data_precision,data_scale,nullable,column_id等
获取表注释：
select * from user_tab_comments
user_tab_comments：table_name,table_type,comments
--相应的还有dba_tab_comments，all_tab_comments，这两个比user_tab_comments多了ower列。
获取字段注释：
select * from user_col_comments
user_col_comments：table_name,column_name,comments