建立测试表
查看版本信息
select version(); 5.7.22
创建父表
drop table if exists Models; CREATE TABLE Models ( ModelID SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, Name VARCHAR(40) NOT NULL, PRIMARY KEY (ModelID) );
创建子表
drop table if exists Orders; CREATE TABLE Orders ( ID SMALLINT UNSIGNED NOT NULL PRIMARY KEY, ModelID SMALLINT UNSIGNED NOT NULL, Description VARCHAR(40), FOREIGN KEY (ModelID) REFERENCES Models (ModelID) ON DELETE cascade );
测试
测试用例-无父表相应数据，先插入子表
insert into Orders(Id,ModelID,Description) values (1,1,'a');
结果：执行失败
异常：[2018-07-31 11:08:01] 23000 cannot add or update a child row: a foreign key constraint fails (bov.orders, constraint orders_ibfk_1 foreign key (modelid) references models (modelid) on delete cascade)
原因：通不过on delete cascade 的外键约束检查
测试用例-先插入主表数据，再插入子表数据
insert into Models(ModelID,Name) values (1,'a'); insert into Orders(Id,ModelID,Description) values (1,1,'a');
结果：执行成功
select * from Models; 1 a select * from Orders; 1 1 a
测试用例-父子表都有数据，删除子表数据
delete from Orders where id = 1;
结果：执行成功
select * from Models; 1 a select * from Orders; 为空
测试用例-父子表都有数据，删除父表书库
delete from Models where ModelID = 1;
结果：执行成功
select * from Models; 为空 select * from Orders; 为空
测试用例-父子表都有数据，更新子表外键
update Orders set ModelID = 3 where ID =1;
结果：执行失败
异常：[2018-07-31 12:33:02] 23000 Cannot add or update a child row: a foreign key constraint fails (bov.Orders, CONSTRAINT Orders_ibfk_1 FOREIGN KEY (ModelID) REFERENCES Models (ModelID) ON DELETE CASCADE)
原因：通不过on delete cascade 的外键约束检查
测试用例-父子表都有数据，更新父表主键
update Models set ModelID = 2 where ModelID =1;
结果：执行失败
异常：[2018-07-31 12:34:24] 23000 Cannot delete or update a parent row: a foreign key constraint fails (bov.Orders, CONSTRAINT Orders_ibfk_1 FOREIGN KEY (ModelID) REFERENCES Models (ModelID) ON DELETE CASCADE)
原因：通不过on delete cascade 的外键约束检查
测试用例-父子表都有数据，更新子表非外键
update Orders set Description = 'b' where ID =1;
结果：执行成功
select * from Orders; 1 1 b
测试用例-父子表都有数据，更新父表非主键
update Models set Name = 'c' where ModelID =1;
结果：执行成功
select * from Models; 1 c
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