Data Model Analysis
1.useryee 和 orders:
useryee --->orders: A user can create multiple orders, one-to-many;orders --->user: An order is only created by one user, one-to-one.
2.orders 和 orderdetail:
orders ---> orderdetail: An order can include multiple order details, because an order can purchase multiple items, and the purchase information of each item is recorded in orderdetail, a one-to-many relationship;orderdetail ---> orders: an order detail Can only be included in one order, one for one.
3.orderdetail 和 products:
orderdetail ---> products: an order detail corresponds to only one product information, one-to-oneproducts ---> orderdetail: a product can be included in multiple order details, one-to-many
4. Tables without relationships at the database level
Then analyze whether there is a business relationship between tables that have no relationship at the database level: A relationshipcan be established between orders and products through the orderdetail table;
user and products have a many-to-many relationship.
5. Individual data sheet data
one-to-one query
1. Add the User property to the Orders class:
2.userMapper.xml:
3.UserMapper.java:
4.UserMapperTest.java:
5. Test results:
[Orders [id=1, userId=1, number=1000010, createTime=Thu Apr 19 17:30:29 CST 2018, note=null, user=User [id=1, name=Lawxf, sex=male, address=null]], Orders [id=2, userId=1, number=1000011, createTime=Thu Apr 19 17:30:29 CST 2018, note=null, user=User [id=1, name=Lawxf, sex=male, address=null]], Orders [id=3, userId=2, number=1000012, createTime=Thu Apr 19 17:30:29 CST 2018, note=null, user=User [id=2, name=Yellia, sex=femal, address=null]]]
one-to-many query
1. Orders add the orderDetail property:
2. userMapper.xml:
3.UserMapper.java:
4. UserMapperTest.java:
5. Test results:
[Orders [id=2, userId=1, number=1000011, createTime=Thu Apr 19 17:30:29 CST 2018, note=null, user=User [id=1, name=Lawxf, sex=male, address=null], orderDetails=[OrderDetail [id=3, ordersId=2, productsId=3, productsNum=4], OrderDetail [id=4, ordersId=2, productsId=2, productsNum=3]]], Orders [id=3, userId=2, number=1000012, createTime=Thu Apr 19 17:30:29 CST 2018, note=null, user=User [id=2, name=Yellia, sex=femal, address=null], orderDetails=[OrderDetail [id=1, ordersId=3, productsId=1, productsNum=1], OrderDetail [id=2, ordersId=3, productsId=2, productsNum=3]]]]