SQL> describe nchar_tst（nchar_tst为表名）

名称                   是否为空? 类型
 ----------------------------------------- -------- ----------------------------
 NAME                        NCHAR(6)
 ADDR                        NVARCHAR2(16)
 SAL                        NUMBER(9,2)

SQL> SELECT DBMS_METADATA.GET_DDL('TABLE','NCHAR_TST') FROM DUAL; 

 CREATE TABLE "SCOTT"."NCHAR_TST"
  (  "NAME" NCHAR(6),
    "ADDR" NVARCHAR2(16

SQL> SET LONG 9999 
SQL> SELECT DBMS_METADATA.GET_DDL('TABLE','NCHAR_TST') FROM DUAL; 

DBMS_METADATA.GET_DDL('TABLE','NCHAR_TST')
------------------------------------------------------------------------------
 CREATE TABLE "SCOTT"."NCHAR_TST"
  (  "NAME" NCHAR(6),
    "ADDR" NVARCHAR2(16),
    "SAL" NUMBER(9,2)
  ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 LOGGING
 STORAGE(INITIAL 12288 NEXT 12288 MINEXTENTS 1 MAXEXTENTS 249 PCTINCREASE 50
 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT) TABLESPACE "SYSTEM"

select t.table_name,t.column_name,t.data_type,t.data_length,t.nullable,t.column_id,c.comments,  
    (SELECT CASE WHEN t.column_name=m.column_name THEN 1 ELSE 0 END FROM DUAL) iskey 
    FROM user_tab_cols t, user_col_comments c, (select m.column_name from user_constraints s, user_cons_columns m  
       where lower(m.table_name)='us_cities' and m.table_name=s.table_name 
       and m.constraint_name=s.constraint_name and s.constraint_type='P') m 
    WHERE lower(t.table_name)='us_cities'  
       and c.table_name=t.table_name  
       and c.column_name=t.column_name  
       and t.hidden_column='NO'  
 order by t.column_id