referential-integrity

问题 Can a single column in a table can be referenced to multiple tables? 回答1: A very late answer, but for whoever is wondering & googeling. YES this can be done, but it is NOT good practice and even though it is quite simple, it will probably blow up in your face if you're not very aware of what you are doing. Not recommended. However, I can see uses. For instance, you have a large table of millions of records, and you want in exceptional cases link to unknown or multiple tables (in which case it

问题 I have 3 tables: Account: Id, Name User: Id, AccountId, Name UserDetail: Id, UserId, Phone Entitites: public partial class Account { public Account() { this.Users = new HashSet<User>(); } public int Id{get;set;} public string Name{get;set;} public virtual ICollection<User> Users{get;set;} } public partial class UserDetail { public int Id{get;set;} public string Phone {get;set;} public virual User User {get;set;} } public partial class User { public User() { this.Accounts = new HashSet<Account

问题 Using SQL SERVER 2005, I have a couple of questions on Replication and referential integrity. 1) Does Replication handle referential integrity? 2) If I do an Insert to Parent table and then to Insert to Child table, in one transaction, on Source DB - will Replicated DB also behave in the same manner? I.e. In Replicated DB record must be present in Master table, before it is referenced in child table? Thanks 回答1: Assuming replication is transactional and you have referential integrity on your

问题 So, I just came across the fact that rails does not support referential integrity regarding foreign keys and was fairly surprised. So, what's the best way to manage this? Is there a "rails" way for dealing with referential integrity? Ideally the app should not have to deal with all this; the db should. I was looking at plugins like foreigner. I wonder if this method has some shortcomings. How is this normally dealt with in rails? 回答1: It's a design decision for Rails ActiveRecord. I consider

问题 I am trying to update an entity in EF6. I have read that if I wish to change a ForeignKey property, I have to then ensure the Navigation Property is the correct one, or set it to null. I have taken the set to null approach, but I still receive the Referential Integrity Constraint Exception: A referential integrity constraint violation occurred: The property value(s) of 'Contact.idContact' on one end of a relationship do not match the property value(s) of 'Entity.id_EntityContactInfo' on the

问题 My Parent class has two child classes: Child and ParentHobby . The Child class has a singular PK and the @OneToMany mapping on it works. The problem is that I don't know how to map it on the ParentHobby class, which has a composite PK. Parent: //this works @OneToMany(cascade = CascadeType.ALL, mappedBy = "parent", fetch = FetchType.EAGER) private List<Child> childList; //this DOES NOT work @OneToMany(cascade = CascadeType.ALL, mappedBy = "parent", fetch = FetchType.EAGER) private List

问题 I've looked at the MySQL 5.1 docs, and still can't figured this out -- that being I noticed a difference between the code I input into MySQL and output code by the system. What is the difference between the code sample 01 and 02, meaning 02 has added CONSTRAINT before FOREIGN KEY -- why, and what's it do? CODE_SAMPLE_01: FOREIGN KEY (TABLE_02_nID_FK__TABLE_01_sID_PK) REFERENCES TABLE_01(TABLE_01_sID_PK), CONTEXT: CREATE TABLE `TABLE_02` ( `TABLE_02_sID_PK` int(8) NOT NULL, `TABLE_02_nID_FK_

问题 Consider a M:M relation that needs to be represented in a Cassandra data store. What M:M modeling options are available? For each alternative, when is it to prefer? What M:M modeling choices have you made in your Cassandra powered projects? 回答1: Instead of using a join table the way you would with an rdbms, you would have one ColumnFamily containing a row for each X and a list of Ys associated with it, then a CF containing a row for each Y and a list of each X associated with it. If it turns

问题 At present we have very little referential integrity, as well as having a number of tables that self-join (and indeed would perhaps better be represented as separate tables or views that joined). The knowledge of how these tables relate to each other is implicit in the logic of the stored procedures rather than explicit in the schema. We are considering changing this. The first step is to actually understand the implicit relationships and document them. So my question is... What is the best

问题 Assuming I have two tables: users and orders . A user has many orders, so naturally there is a foreign key user_id in my orders table. What is the best practice in rails (in terms of speed, style and referential integrity) to ensure that if a user is deleted, all dependent orders are also deleted? I am considering the following options: Case 1. Using :dependent => :destroy in the user model Case 2. Defining the table orders in postgres and writing user_id integer REFERENCES users(id) ON