SELECT T1.TABLE_NAME,
T1.COLUMN_NAME,
T1.DATA_TYPE || '(' || T1.DATA_LENGTH || ')',
T2.COMMENTS
FROM USER_TAB_COLS T1, USER_COL_COMMENTS T2
WHERE T1.TABLE_NAME = T2.TABLE_NAME
AND T1.COLUMN_NAME = T2.COLUMN_NAME
AND T1.TABLE_NAME =upper('tc_plantask') ;

获取表： 
select table_name from user_tables; //当前用户的表        table_name,tablespace_name,last_analyzed等 

select table_name from all_tables; //所有用户的表           ower,table_name,tablespace_name,last_analyzed等 

select table_name from dba_tables; //包括系统表       ower,table_name,tablespace_name,last_analyzed等 

select table_name from dba_tables where owner='用户名' 

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