-- 创建customers表

prompt
prompt 创建customers表 
create table customers 
(
    pin_number number(6)
);

/*
-- 添加主健,因为customers表只有一个子段，所以下面代码汇报错:ORA-02260: table can have only one primary key 
prompt 
prompt 添加主健
alter table customers add constraint customers_pk primary key (pin_number);
/
*/
