foreign-key-relationship

问题 I'm working on a little support (ticket) system. My tables are tickets and ticket_replies. Design of tickets table is id|user_id|title|... Design of ticket_replies looks like: id|ticket_id|... The foreign key I added looks like this: ALTER TABLE `ticket_replies` ADDFOREIGN KEY (`ticket_id`) REFERENCES `sampleauth`.`tickets`(`id`) ON DELETE CASCADE ON UPDATE CASCADE; Now when I delete a "ticket" in the "ticket" table it gets deleted in "ticket_replies" too. The other way this doesn't work, all

问题 I have this image table , image_id image_title image_description image_source and I want this image table to associate with page table and sometimes with comment table page table, page_id ... ... comment table, comment_id ... ... Should I put the foreign key of page_id and comment_id in image table? image_id image_title image_description image_source page_id comment_id Or should I create a map table for each purpose? a map table for image and page image_id page_id and another map table for

问题 i am using Entity Framework with code first approach. In my onModelCreating I am creating my tables with keys and relationships (I am using Fluent API approach, not data annotations). But when I try to generate my model using Update-Database command I receive following error Introducing FOREIGN KEY constraint 'FK_customers.invoices_customers.billingCenters_billingCenterId' on table 'invoices' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or

问题 Following on from earlier posts today: Entity framework one to zero or one relationship without navigation property Understanding ForeignKey attribute in entity framework code first I'm now trying to configure the following relationships: Item1 has optional RawData Item2 has optional RawData Item3 has optional RawData RawData must be attached to either Item1, Item2 or Item3 - it would not be expected to exist on its own. Current structure is: class ItemX { [Key] public int Id { get; set; }

问题 The database looks like this: CREATE TABLE artists ( artist_id SERIAL PRIMARY KEY, artist TEXT UNIQUE NOT NULL ); CREATE TABLE artistalias ( artistalias_id SERIAL PRIMARY KEY, artist_id SERIAL REFERENCES artists (artist_id), alias TEXT UNIQUE NOT NULL ); CREATE TABLE songs ( song_id SERIAL PRIMARY KEY, song TEXT NOT NULL, artist_id SERIAL REFERENCES artists (artist_id) ); one artist can have zero, one or many aliases one alias belongs to exactly one artist one song has one artist one artist

问题 I'm having lots of trouble with a little prototype I'm trying to build. The problem involves two entities. But to understand it, I will need to describe a few others. In terms of the database structure, it can be described as follows: Person ---------------- id Integer PK surname VARCHAR givenNames VARCHAR TypedIdentifier ---------------- idCode VARCHAR PK FK (IdType.code) idVal VARCHAR PK person Integer FK (Person.id) IdType ------ code VARCHAR PK IdDescription ---------- code VARCHAR PK FK

问题 This may have a really easy answer. I have done much database stuff for a while. I am trying to get the auto_increment value from one table inserted into the value on another table. is there an easy way of doing this. For eg i have done: CREATE TABLE table_a ( id int NOT NULL AUTO_INCREMENT, a_value varchar(4), PRIMARY KEY (id) ); CREATE TABLE table_b ( id int NOT NULL, b_value varchar(15), FOREIGN KEY (id) REFERENCES table_a (id) ); Now i want to insert values into the table but I would like

问题 I have two related tables: [GameDataGroup] with PK [Arena_GameData] with FK I try to execute query: DELETE FROM [ACP_MAIN_STABLE_DB_content].[dbo].[GameDataGroup] WHERE [key] LIKE '%' + '_test_group' + '%' And have a message: The DELETE statement conflicted with the REFERENCE constraint "FK__Arena_GameData__GameDataGroup". The conflict occurred in database "ACP_MAIN_STABLE_DB_content", table "dbo.Arena_GameData", column 'gameDataGroupId'. While there is no related data in "dbo.Arena_GameData"

问题 I have the following LINQ to SQL EF classes: with the foreign key relationship on SessionId (primary table WebinarSession ). I would like, by using lambdas to select all the WebinarSession rows that concern a specific product line. I put as example this code that of course DOES NOT WORK (it would owrk with Single inseatd of Where but it is not applicable because I have mulitple instances matching the condition): SessionId = _webinarRecordingsDB.WebinarSessions.Where(m => m.SessionId == m

问题 I have a Post model, and a Comment model that belongs to Post. I was able to display the Post in the home view corresponding to the home controller and home action and the User/show view. Thus, in the home and user views, the posts are listed in order of creation time. I was also able to have a post form in both the user and home views and a comment form in the home and user views. The problem arises when I try to display the comment underneath each displayed Post in the home and user views.