请大神帮忙
alter table HOUSE
drop constraint FK_HOU_ST;
alter table HOUSE
drop constraint FK_HOU_US;
alter table HOUSE
drop constraint FK_HOU_TY;
alter table STREET
drop constraint FK_STR_DI;
drop table DISTRICT cascade constraints;
drop table HOUSE cascade constraints;
drop table STREET cascade constraints;
drop table TYPES cascade constraints;
drop table USERS cascade constraints;
drop sequence SEQ_ID;
create sequence SEQ_ID;
create table DISTRICT (
ID NUMBER(4) not null,
NAME NVARCHAR2(50) not null,
constraint PK_DISTRICT primary key (ID)
);
create table HOUSE (
ID NUMBER(6) not null,
USER_ID NUMBER(4),
TYPE_ID NUMBER(4),
TITLE NVARCHAR2(50),
DESCRIPTION NVARCHAR2(2000),
PRICE NUMBER(10, 2),
PUBDATE DATE,
FLOORAGE NUMBER(4),
CONTACT NVARCHAR2(100),
STREET_ID NUMBER(4),
constraint PK_HOUSE primary key (ID)
);
create table STREET (
ID NUMBER(4) not null,
NAME NVARCHAR2(50) not null,
DISTRICT_ID NUMBER(4),
constraint PK_STREET primary key (ID)
);
create table TYPES (
ID NUMBER(4) not null,
NAME NVARCHAR2(50) not null,
constraint PK_TYPES primary key (ID)
);
create table USERS (
ID NUMBER(4) not null,
NAME NVARCHAR2(50) not null,
PASSWORD NVARCHAR2(50) not null,
TELEPHONE NVARCHAR2(15),
USERNAME NVARCHAR2(50),
ISADMIN NVARCHAR2(2),
constraint PK_USERS primary key (ID)
);
alter table HOUSE
add constraint FK_HOU_ST foreign key (STREET_ID)
references STREET (ID);
alter table HOUSE
add constraint FK_HOU_US foreign key (USER_ID)
references USERS (ID);
alter table HOUSE
add constraint FK_HOU_TY foreign key (TYPE_ID)
references TYPES (ID);
alter table STREET
add constraint FK_STR_DI foreign key (DISTRICT_ID)
references DISTRICT (ID);
请问这段代码哪里有问题