foreign-key-relationship

问题 Sorry for the nebulous title, it's hard to describe this in a single line: I have 2 entities User and UserAddress , where User has 2 foreign keys DefaultInvoiceAddressId and DefaultDeliveryAddressId and UserAddress has a UserId foreign key. The user object has navigation properties for the default addresses ( DefaultInvoiceAddress and DefaultDeliveryAddress ) as well as one for all of his addresses: AllAddresses . The mapping etc. works, creating and updating users and addresses works too.

问题 I am new to Backbone-relational, I am not sure what is the right way to use HasMany. I have a Parent model which have many children (by "many" I mean thousands of children). In order to avoid performance issue, I query children by their foreign key: /child/?parent=1 , instead of create a huge list of child_ids in Parent . But seems this is not the way Backbone-relational work. So I am wondering what is the right way to handle this. 1, Change my json api to include list of child id in parent,

问题 We have a system that allows Administrators to build out new content types within the system, including foreign key linkages to other tables. The Admin can then rebuild the database, at which point it creates the tables and all the necessary relationships, then rebuilds the EDMX and recompiles everything. Works like a champ (I didn't write it or I might know the answer to this). One drawback that we have is when a user goes to delete a record that may be linked to by an item in another table.

问题 I know the purpose of "Enforce foreign key constraint" in RDBMS. But is there any benefit when it's set to "NO" ? 回答1: In normal production, this setting should never be set to NO . But: when you're developing, or restructuring a database, or when you do e.g. a large bulk load of data that you'll need to "sanitize" (clean up), then it can make sense to turn off foreign key constraints to allow "non-valid" data to be loaded into a table. Of course, as I said - you shouldn't keep that setting

问题 Similar but NOT IDENTICAL to SQL Server 2000 - Query a Table’s Foreign Key relationships I need a T-SQL statement that will work SQL 2000 that given a table name, will return the foreign key relationships for that table e.g. Table MyFristTable has a foreign key to MySecondTable, where MyFirstTable.ColA must be in MySecondTable.ColB. I'd be delighted, if the sql statement (or stored proc) is ran for MyFirstTable and returned a result set on the lines of Column | FK_Table | FK_COLUMN ----------

问题 Similar but NOT IDENTICAL to SQL Server 2000 - Query a Table’s Foreign Key relationships I need a T-SQL statement that will work SQL 2000 that given a table name, will return the foreign key relationships for that table e.g. Table MyFristTable has a foreign key to MySecondTable, where MyFirstTable.ColA must be in MySecondTable.ColB. I'd be delighted, if the sql statement (or stored proc) is ran for MyFirstTable and returned a result set on the lines of Column | FK_Table | FK_COLUMN ----------

问题 I have table 1 with a primary key user_id and table 2 where user_id is a foreign key. Only 1 record per user_id can exist in table 2, and no record can exist without it. QUESTION: Can user_id in table 2 be both foreign and primary key at the same time, and if yes, is it a good idea, what are pros/cons? 回答1: Yes, you can do this (and you should, from a database design point of view). However, consider what it means if user_id is the primary key on table 2. You are in effect saying that each

问题 I have the following models Category: <?php class Category extends Eloquent { protected $table = "category"; protected $fillable = array('title','parent','metatit','metadsc','metake','metaurl','image'); public function categoryitems(){ return $this->hasMany('CategoryItem','catid'); } public function parent(){ return $this->hasMany('category','parent'); } public function child(){ return $this->belongsTo('Category','parent'); } } Need to set a 1 to many relationship in the category table Ex

问题 like so: Table-student: sID | name 1 -----susan 2 -----morgan 3 -----Ian 4 -----james Primary key = sID the other table like so: Table- friends friendsID | personA | personB 1-----------1-----------3 2------------1-----------2 3-------------2-----------3 4-------------3------------4 Where Primary Key is: friendsID, personA, personB Foreign Key = personA, personB which both refer to sID in students table I want a way of querying the friends table in such a way that the personA and personB

问题 I'm using ORMLite, trying to use the ForeignCollectionKey but I got the following error : Internal DAO object is null. LazyCollections cannot be used if they have been deserialized. I've my object named Zone : public class Zone implements Serializable { private static final long serialVersionUID = 1L; public static final String ZONE_ID = "id"; public static final String ZONE_PARENT_ID = "parentZoneId"; @DatabaseField(generatedId=true) private int id; @DatabaseField() String name;