我如何为给定的多个相关类创建表? [英] How i can make tables for the given many to many related classes ?
问题描述
我有三个班级的情景。我打算为它建立数据库。它们之间的关系是:
1客户与许多物品和许多dv-vouchers相关。 br />
1项与许多客户和许多dv-vouchers相关。
1 dv-vouchers与1位顾客和许多物品有关。
< pre lang =xml> public Customer
{
int cust_id;
list < items > items;
list < dvouchers > dvouchers;
}
公共项目
{
int itm_id;
list < 客户 > 客户;
list < dvouchers > dvouchers;
}
public dvouchers
{
int dv_id;
客户客户;
list < items > items;
}
首先,上述类的数据库表的设计以及fk_constraints和关系表是什么?
Second我是否需要同时执行插入和更新db表中的关系表?请帮助。
足够简单。
第二个问题的答案是肯定的。CREATE TABLE customers(
CustomerID NUMBER( 8 )
)
/
ALTER TABLE 客户 ADD CONSTRAINT customers_pk PRIMARY KEY (CustomerID)
/
CREATE TABLE 项目(
ItemID NUMBER( 8 )
)
/
ALTER TABLE 项 ADD CONSTRAINT Items_pk PRIMARY KEY (CustomerID)
/
创建 TABLE dvouchers(
DVoucherID NUMBER( 8 ),
CustomerID NUMBER( 8 )
)
/
ALTER 表 dvouchers ADD CONSTRAINT dvouchers_pk PRIMARY KEY (CustomerID)
/
ALTER TABLE dvouchers
ADD CONSTRAINT dvouchers_Customers_FK FOREIGN KEY (
CustomerID
) REFERENCES 客户(
CustomerID
)
/
CREATE TABLE CustomerItems(
CustomerID NUMBER( 8 ),
ItemID NUMBER( 8 )
)
/
ALTER TABLE CustomerItems
ADD CONSTRAINT CustomerItems_pk PRIMARY < span class =code-keyword> KEY (
CustomerID,
ItemID
)
/
ALTER 表 CustomerItems
ADD CONSTRAINT CustomerItems_Customer_FK FOREIGN KEY (
CustomerID
) REFERENCES 客户(
CustomerID
)
/
ALTER TABLE CustomerItems
ADD CONSTRAINT CustomerItems_Items_FK < span class =code-keyword> FOREIGN KEY (
ItemID
)参考项目(
ItemID
)
/
CREATE TABLE dvoucherItems(
dvoucherID NUMBER( 8 ),
ItemID NUMBER( 8 )
)
/
ALTER TABLE dvoucherItems
ADD CONSTRAINT dvoucherItems_pk PRIMARY KEY (
dvoucherID,
ItemID
)
/
ALTER TABLE dvoucherItems
ADD CONSTRAINT dvoucherItems_dvouchers_FK FOREIGN KEY (
dvoucherID
) REFERENCES dvouchers(
dvoucherID
)
/
ALTER 表 dvoucherItems
ADD CONSTRAINT dvoucherItems_Items_FK FOREIGN KEY (
ItemID
) REFERENCES 项目(
ItemID
)
/
I have a scenario of of three classes .I am planning to make the database for it .The relationship between them is :
1 customer is related with many items and many dv-vouchers.
1 item is related with many customer and many dv-vouchers.
1 dv-vouchers is related with 1 customer and many items .
public Customer
{
int cust_id;
list<items> items;
list<dvouchers> dvouchers;
}
public items
{
int itm_id;
list<Customer> customers;
list<dvouchers> dvouchers;
}
public dvouchers
{
int dv_id;
Customer customer;
list<items> items;
}
First of all what can be the design of database tables for above classes along with fk_constraints and relationship tables ?
Second Do I need to do both an Insert and Update the relationship tables along db table ? Please Help .
Simple enough.
The answer to your second question is Yes.CREATE TABLE customers ( CustomerID NUMBER(8) ) / ALTER TABLE customers ADD CONSTRAINT customers_pk PRIMARY KEY (CustomerID) / CREATE TABLE Items ( ItemID NUMBER(8) ) / ALTER TABLE Items ADD CONSTRAINT Items_pk PRIMARY KEY (CustomerID) / CREATE TABLE dvouchers ( DVoucherID NUMBER(8), CustomerID NUMBER(8) ) / ALTER TABLE dvouchers ADD CONSTRAINT dvouchers_pk PRIMARY KEY (CustomerID) / ALTER TABLE dvouchers ADD CONSTRAINT dvouchers_Customers_FK FOREIGN KEY ( CustomerID ) REFERENCES Customers ( CustomerID ) / CREATE TABLE CustomerItems ( CustomerID NUMBER(8), ItemID NUMBER(8) ) / ALTER TABLE CustomerItems ADD CONSTRAINT CustomerItems_pk PRIMARY KEY ( CustomerID, ItemID ) / ALTER TABLE CustomerItems ADD CONSTRAINT CustomerItems_Customer_FK FOREIGN KEY ( CustomerID ) REFERENCES Customers ( CustomerID ) / ALTER TABLE CustomerItems ADD CONSTRAINT CustomerItems_Items_FK FOREIGN KEY ( ItemID ) REFERENCES Items ( ItemID ) / CREATE TABLE dvoucherItems ( dvoucherID NUMBER(8), ItemID NUMBER(8) ) / ALTER TABLE dvoucherItems ADD CONSTRAINT dvoucherItems_pk PRIMARY KEY ( dvoucherID, ItemID ) / ALTER TABLE dvoucherItems ADD CONSTRAINT dvoucherItems_dvouchers_FK FOREIGN KEY ( dvoucherID ) REFERENCES dvouchers ( dvoucherID ) / ALTER TABLE dvoucherItems ADD CONSTRAINT dvoucherItems_Items_FK FOREIGN KEY ( ItemID ) REFERENCES Items ( ItemID ) /
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