foreign-key-relationship

问题 I'm converting an app from native mysqli calls to PDO. Running into an error when attempting to insert a row into a table with a foreign key constraint. Note: this is a simplified test case and should not be copy/pasted into a production environment. Info PHP 5.3, MySQL 5.4 First, here are the tables: CREATE TABLE `z_one` ( `customer_id` int(10) unsigned NOT NULL DEFAULT '0', `name_last` varchar(255) DEFAULT NULL, `name_first` varchar(255) DEFAULT NULL, `dateadded` datetime DEFAULT NULL,

问题 Suppose I have a table "nodes" where I store a tree. Each node has a primary key id and a column parent_id. Of course, I want to access a parent attribute of each node instance, that is, a relation. One might try: import sqlalchemy, sqlalchemy.orm, sqlalchemy.ext.declarative engine = sqlalchemy.create_engine('sqlite:///PATHTOMYDATABASE', echo=True) Base = sqlalchemy.ext.declarative.declarative_base() class Node(Base): __tablename__ = "nodes" id = sqlalchemy.Column(sqlalchemy.Integer, primary

问题 I'm dealing with a set of tables in a database that appear to have a circular relationship (see image). This is the ARTS database if that is of any help to anyone. A user signing on: a) must create a (insert into) session, which in turn needs a SessionStartTransactionID (=SignOnTransaction) b) a SignOnTransaction is a type of ControlTransaction c) a ControlTransaciton is a type of Transaction d) a Transaction needs a reference to an existing Session (along with Operator, etc.) Note: The

问题 Here's the entites and context code: public class Family { public int FamilyID { get; set; } public String address { get; set; } public virtual ICollection<Member> FamilyMembers { get; set; } } public class Member { [Index("MemberUniqueID", IsUnique = true)] public int MemberID { get; set; } [StringLength(50)] [Index("MemberUniqueIndex", 1, IsUnique = true)] public String name { get; set; } [StringLength(50)] [Index("MemberUniqueIndex", 2, IsUnique = true)] public String surname { get; set; }

问题 I want to delete a row/tuple from a parent table, but it is throwing an error message because it has a FOREIGN KEY reference in its child table. However, in my case I want to delete the record only from the parent table and maintain the data in the child table . Is it possible to achieve this? I know the usage of ON DELETE CASCADE, but I want to know if there is a solution for the secenario I described? 回答1: It is possible with some agreements in your data. To maintain child table data you'll

问题 I am trying to create a DbSyncForeignKeyConstraint to a table with a composite Primary Key but, I keep getting errors. Here is some sample code to demonstrate what I am doing: EXAMPLE TABLES: USE [TempTest] GO CREATE TABLE [dbo].[Users]( [UserId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ( [UserId] ASC ) WITH ( PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON ) ON [PRIMARY] ) ON [PRIMARY] CREATE

问题 I'm using CakeDC-Users plugin. <?php class Post extends AppModel { public $useTable='posts'; public $belongsTo = array('User'); public $hasMany=array('Comment'); } I had to use paginate: $allposts=$this->paginate('Post'); I can get the user_id in this way: foreach ($allposts as $post) { debug($post['Post']['user_id']); But i need the username not the user_id. How can i get username? 回答1: The containble feature of CakPHP hides all associated models by default: http://book.cakephp.org/2.0/en

问题 I am receiving the following error: ValueError: Cannot assign "u'ben'": "Entry.author" must be a "MyProfile" instance. From this line: form.author = request.session['username'] Note: Entry.author is a foreign key as seen below. models.py class MyProfile(models.Model): user = models.CharField(max_length=16) first_name = models.CharField(max_length=30) last_name = models.CharField(max_length=30) def __unicode__(self): return u'%s %s %s' % (self.user, self.firstname, self.lastname) class Entry

问题 I have two table second and third second_id(PRIMARY KEY) second_name 1 ......... 2 ....... 3 ......... third_id(PRIMARY KEY) third_name second_id(FOREIGN KEY for second.second_id) 1 ..... 1 2 ..... 1 3 ..... 1 4 ..... 2 5 ..... 2 Now i want to delete a row from second where second_id=2 ( DELETE FROM second WHERE second_id=2 ) but it does not work. It says Successful 0 row(s) affected What is more is, it happened after i append a foreign key to third.second_id (i added foreign key after table

问题 I'm attempting to setup a foreign key in table cell_lines that will reference the topographic_region column of the composite primary key in table topographic_regions . Each time I run the last three lines of code trying to add the foreign key, I receive Error Code 1215: cannot add foreign key constraint. Now, the foreign key column name ( topographic_region ) in cell_lines only matches one of the composite primary key column names in topographic_regions , the other composite primary key