相关疑难解决方法(0)

考虑以下设计：

CREATE TABLE dbo.Farmers
(
    FarmerName varchar(10) NOT NULL
        PRIMARY KEY 
);

CREATE TABLE dbo.FarmEquipment
(
    FarmEquipmentName varchar(10) NOT NULL
        PRIMARY KEY 
    , CreatorFarmer varchar(10) NOT NULL
        FOREIGN KEY REFERENCES dbo.Farmers(FarmerName)
        ON UPDATE CASCADE
        ON DELETE CASCADE
);

CREATE TABLE dbo.Fields
(
    FieldName varchar(10) NOT NULL
    , OwnerFarmer varchar(10) NOT NULL
        FOREIGN KEY REFERENCES dbo.Farmers(FarmerName)
        ON UPDATE CASCADE
        ON DELETE CASCADE
    , FarmEquipment varchar(10) NOT NULL
        FOREIGN KEY REFERENCES dbo.FarmEquipment(FarmEquipmentName)
        ON UPDATE CASCADE
        ON DELETE CASCADE
);

用例：

• 农民乔拥有土地。
• 农民泰德拥有土地。 …