foreign-keys

Just installed MySQL 5.5 on mac os x 10.6 and am having a strange issue on many tables. Below is an example. Inserting a row fails with a foreign key constraint when it shouldn't. The foreign key it references does exist. Any ideas? mysql> show create table Language; +----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I'm piecing together an image website. The basic schema's pretty simple MySQL, but I'm having some trouble trying to represent possible admin flags associated with an image ("inappropriate", "copyrighted", etc.). My current notion is as follows: tblImages ( imageID INT UNSIGNED NOT NULL AUTO_INCREMENT, ... ); tblImageFlags ( imageFlagID INT UNSIGNED NOT NULL AUTO_INCREMENT, imageID INT UNSIGNED NOT NULL, flagTypeID INT UNSIGNED NOT NULL, resolutionTypeID INT UNSIGNED NOT NULL, ... ); luResolutionTypes ( resolutionTypeID INT UNSIGNED NOT NULL AUTO_INCREMENT, resolutionType VARCHAR(63) NOT NULL,

I have an example situation: parent table has a column named id , referenced in child table as a foreign key. When deleting a child row, how to delete the parent as well if it's not referenced by any other child? In PostgreSQL 9.1 or later you can do this with a single statement using a data-modifying CTE . This is generally less error prone. It minimizes the time frame between the two DELETEs in which a race conditions could lead to surprising results with concurrent operations: WITH del_child AS ( DELETE FROM child WHERE child_id = 1 RETURNING parent_id, child_id ) DELETE FROM parent p USING

We are using EF 4.1 and the fluent API to get data from a legacy database (that we are not permitted to change). We are having a problem creating a relationship between two tables where the related columns are not primary and foreign keys. With the classes below, how would we configure the one-to-many relationship between Report and RunStat such that Report.RunStats would return all of the RunStat entities where the ReportCode fields are equal? public class Report { [Key] public int ReportKey { get; set; } public string Name { get; set; } public int ReportCode { get; set; } // Can we associate

It appears that SQLite does not enforce foreign keys by default. I'm using sqlitejdbc-v056.jar and I've read that using PRAGMA foreign_keys = ON; will turn on foreign key constraints, and that this needs to be turned on in a per-connection basis. My question is: what Java statements do I need to execute to turn on this command? I've tried: connection.createStatement().execute("PRAGMA foreign_keys = ON"); and Properties properties = new Properties(); properties.setProperty("PRAGMA foreign_keys", "ON"); connection = DriverManager.getConnection("jdbc:sqlite:test.db", properties); and connection =

I am attempting to create a DB for my app and one thing I'd like to find the best way of doing is creating a one-to-many relationship between my Users and Items tables. I know I can make a third table, ReviewedItems , and have the columns be a User id and an Item id, but I'd like to know if it's possible to make a column in Users , let's say reviewedItems , which is an integer array containing foreign keys to Items that the User has reviewed. If PostgreSQL can do this, please let me know! If not, I'll just go down my third table route. No, this is not possible. PostgreSQL is a relational DBMS,

In this document (scroll down to the Unidirectional section): http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-mapping-association-collections it says that a unidirectional one-to-many association with a join table is much preferred to just using a foreign key column in the owned entity. My question is, why is it much preferred? Consider the situation where the owned entity type can also be owned by another parent entity type. Do you put foreign key references in the owned table to both parent tables? What if you have three parent types? It just doesn't scale