foreign-keys

问题 I am trying to do an Ordering System where you can put many Products in one order. I have very little knowledge about this and this is where i am now There are 3 tables, Product table,Order table and the Order-products table. I really don't know if this is right as i am beginner especially on foreign keys. What I want to achieve is you can order many products and put that products into one "OrderID" like this example in pic below. This are my only codes. Sorry but i am really lost at this.

问题 I'm working with a table that has an integer column and a foreign key. This integer has to be incremental, but it has to start again in 1 when the foreign key is changed. Example: Foreign 1, int col : 1 , 2 , 3... Foreign 2, int col: 1 ,2 , 3, 4, 5 ... Foreign 3, int col: 1, 2 This is my mapping so far: (Of course this doesn't does the trick) public class Documento implements ModelEntity{ private static final long serialVersionUID = 11233L; /*PK*/ @Id @Column(name = "id") @GeneratedValue

问题 I am trying to run a query: INSERT INTO `ProductState` (`ProductId`, `ChangedOn`, `State`) SELECT t.`ProductId`, t.`ProcessedOn`, \'Activated\' FROM `tmpImport` t LEFT JOIN `Product` p ON t.`ProductId` = p.`Id` WHERE p.`Id` IS NULL ON DUPLICATE KEY UPDATE `ChangedOn` = VALUES(`ChangedOn`) (I am not quite sure the query is correct, but it appears to be working), however I am running into the following issue. I am running this query before creating the entry into the 'Products' table and am

问题 We cannot run the query below. We have another table named "person" and it has a primary key person_id. As you can see, we are trying to get this column as our (customers table's) foreign key. phpMyAdmin returns #1064 syntax error. What's going wrong here? CREATE TABLE IF NOT EXISTS `resort`.`customers` ( `person_id` VARCHAR(45) NOT NULL , `cid` INT UNSIGNED NOT NULL AUTO_INCREMENT , UNIQUE INDEX `person_id_UNIQUE` (`cid` ASC) , PRIMARY KEY (`person_id`) , UNIQUE INDEX `person_id_UNIQUE` (

问题 I have one parent resource which can have more than one children of one attrbiute and one than more children of other attribute. They look like this: class RouteResource(ModelResource): creator = fields.ForeignKey(UserProfileResource, 'creator', full=True) towns = fields.ToManyField(TownResource, 'towns', full=True, null=True) model is: class Route(models.Model): name = models.CharField(max_length=50) description = models.CharField(max_length=500) average_rate = models.FloatField(null=True,

问题 @Entity(tableName = "subscription") data class Subscription( @PrimaryKey val planId: Int, @ColumnInfo(name = "plan_name") val planName: String? = null, @ColumnInfo(name = "plan_description") val planDescription: String? = null, @ColumnInfo(name = "plan_reg_fee") val planRegFee: String? = null, @ColumnInfo(name = "plan_monthly_charge") val planMonthlyCharge: String? = null ) data class Benefit( @ColumnInfo(name = "benefit_id") val benefitId: Int? = null, @ColumnInfo(name = "benefit_code") val

问题 I have a table 'user_plays_track' that keeps track of how many times a user has 'played' a track. I use the following query to either insert a new track a user has played, or update the number of times an existing track has been played: INSERT INTO user_plays_track (user_id, track_id) VALUES (x,y) ON duplicate key UPDATE play_count = play_count+1 Here is the structure of my table: user_id track_id play_count 1 5 2 4 2 1 3 5 7 From this information, I can infer things such as the total number

问题 I have an entity Villa, and I want this Entity to contain other Villas which have the same 'complex' ( Varchar(255) ). class VillasTable extends Table { /** * Initialize method * * @param array $config The configuration for the Table. * @return void */ public function initialize(array $config) { $this->table('villas'); $this->displayField('name'); $this->primaryKey('id'); $this->hasMany('Complexs', [ 'className' => 'Villas', 'foreignKey' => false, 'propertyName' => 'complexs', 'conditions' =>

问题 In Laravel 4, how can I add a foreign key constraint in a migration? In the migration for mytable (which references foreigntable ): // add Column $table ->string( 'foreigntable_id', 6 ); // add FK $table ->foreign( 'foreigntable_id' ) ->references( 'id' ) ->on( 'foreigntable' ); Error: [Exception] SQLSTATE[HY000]: General error: 1005 Can't create table 'mydb.#sql-1a24_2 1a' (errno: 150) (SQL: alter table `mytable` add constraint mytable_foreigntable_id_foreign foreign key (`foreigntable_id`)

问题 I am developing an ASP.NET MVC project. I am using Entity Framework code first approach to interact with database. But I am having a problem with setting on cascade delete for self-reference foreign key for an entity. This is my entity class with self reference foreign key public class Category { public int Id { get; set; } [Required] [MaxLength(50)] public string Name { get; set; } [MaxLength(55)] public string MmName { get; set; } public int? ParentId { get; set; } [ForeignKey("ParentId")]