通过在ParentEntity的child属性上使用@JoinColumn注解,设置nullable属性为true,并且设置onDelete属性为ReferentialAction.SET_NULL,即可将操作"on delete set null"设置为外键。 这样,在删除ParentEntity的记录时,如果存在关联的ChildEntity记录,将会将外键字段child_id设
On Update表示主键表中被参考字段的值被更新时,On Delete表示主键表中被参考字段的值被删除时。 语法: foreign key (foreign_key_id) references table(primary_key_id) on update/delete parameter 其中parameter有no action , set null , set default ,cascade四个选项,分别表示: 1.no action 表示 不做任何...
ON DELETE CASCADE无法在MySQL中运行 在MySQL中,ON DELETE CASCADE是一个用于定义外键约束的选项,它可以在删除主表中的行时自动删除或更新关联的从表中的行。当主表中的行被删除时,从表中的相关行也会被删除。 以下是一个简单的示例: 代码语言:sql 复制 CREATETABLEusers(idINTPRIMARYKEY,nameVARCHAR(50));CREA...
"kodeine/laravel-meta": "^2.0" after that, runcomposer updateto upgrade the package. Upgrade notice Laravel meta 2 has some backward incompatible changes that listed below: Laravel 7 or lower not supported. Removed the following methods:__get,__set,__isset. If you have defined any of these...
Usually, we need to update the Elasticsearch index when records in the database are created, updated or deleted; use the index_document, update_document and delete_document methods, respectively: Article::first()->indexDocument(); => ['ok'=>true, ..."_version"=>2] Note thatthisimplementa...
DB::update('update users set name = "laravelAcademy" where name = ?',['Academy'] );//返回受影响的行数 DB::delete('delete from users where name = ?',['张三']);//返回受影响的行数 DB::statement('drop table users');//删除用户表 ...
public function up(): void { Schema::create('exam_histories', function (Blueprint $table) { $table->id(); $table->foreignId('user_id')->constrained()->onDelete('cascade'); $table->foreignId('assessment_id')->constrained()->onDelete('cascade'); $table->foreignId('quiz_...
I'm new to app development, new to Laravel and new to Homestead. I've just successfully served up my first 'hello world' home page via Vagrant/Homestead. I have a few of questions: Assuming my config ... Set Iterator & NullPointerException ...
I use Laravel sanctum SPA specifically through sessions and cookies when logging out the user_id field in Database is not set to null after the user logs out, but it remains until another request comes with the same session and same SANCTUM_STATEFUL_
delete update MyISAM和InnoDB MyISAM InnoDB 注意事项 事务提交后,才会释放锁 死锁 日志 redo log(重做日志,存储引擎模块): 作用:确保事务的持久化 事务开始的时候记录 bin log(归档日志,server层面): 作用:复制和恢复数据(主从复制) 事务提交的时候记录 ...