Foreign-key, or referential-integrity. Value-based constraints. relation> (<attributes>) Referenced attributes must be declared PRIMARY KEY or UNIQUE Enforcing Foreign-Key Constraints If there is a foreign-key constraint from relation R to relation S, two violations are (动作,也就是触发器被触发后需要执行的SQL语句) Preliminary Example: A Trigger Instead of using a foreign-key constraint
<joined-subclass name="com.b510.examples.PostDelivery" table="post_mail"> <key column="id" foreign-key joined-subclass name="com.b510.examples.ExpressDelivery" table="express_mail"> <key column="id" foreign-key
pk_users" PRIMARY KEY, btree (user_id) "unq_users_0" UNIQUE CONSTRAINT, btree (user_name, user_type) Foreign-key | character varying(32) | not null Indexes: "pk_host_version" PRIMARY KEY, btree (id) Foreign-key
-- name:当前类的属性名 column:从表中的外键名 foreign-key:主表中的被参照字段 property-ref:主表中被参照字段的属性名 <set name="cities" cascade="all" lazy="true" inverse="true"> <key column="provincecode" foreign-key
In this case, gap locking is disabled for searches and index scans and is used only for foreign-key constraint 文档中说的很清楚,当事务的隔离级别设置为RC时,普通的searches和index scan是不会产生Gap锁的,但是foreign-key约束检查和唯一键冲突检查仍然有可能会产生Gap锁。
Under these circumstances, gap locking is disabled for searches and index scans and is used only for foreign-key
In this case, gap locking is disabled for searches and index scans and is used only for foreign-key constraint
加锁的select, update, delete等语句,除了在外键约束检查(foreign-key constraint checking)以及重复键检查(duplicate-key checking
OptExpression mvExpression) { // short circuit for tables without foreign-key
In this case, gap locking is disabled for searches and index scans and is used only for foreign-key constraint
四,读提交(Read Committed, RC) 这是互联网最常用的隔离级别,在RC下: (1)普通读是快照读; (2)加锁的select, update, delete等语句,除了在外键约束检查(foreign-key
img First of all,什么是物理外键,好吧虽然基础,但是我们不能跑偏,所以啰嗦的虫子还是喜欢把概念链接给贴上,维基百科更详细,不过这个逼就不装了,留给你们吧 Foreign-Key(w3school
官方文档后面还有一句: In this case, gap locking is disabled for searches and index scans and is used only for foreign-key
如果设置为1,会禁用gap锁,但对于外键冲突检测(foreign-key constraint checking)或者重复键检测(duplicate-key checking)还是会用到gap锁。
AbstractFlushingEventListener.java /** * Execute all SQL (and second-level cache updates) in a special order so that foreign-key
Under these circumstances, gap locking is disabled for searches and index scans and is used only for foreign-key
Under these circumstances, gap locking is disabled for searches and index scans and is used only for foreign-key
department(dept_Id,dept_name, building, budget) 外码约束(foreign-key constarint)表示,在任何数据库实例中,r1的每个元组对A的取值必须也是
One or more rows contain values violating non-null, unique, or foreign-key constraints.'
Foreign-key constraints: "c_items_1" FOREIGN KEY (hostid) REFERENCES hosts(hostid) ON DELETE CASCADE