INSERT and UPDATE performance varies little: it will be almost same for (INT) and (INT, INT) keys. SELECT performance of composite PRIMARY KEY depends on many factors. If your table is InnoDB, then the table is implicitly clustered on the PRIMARY KEY value. That means that searches for both values will be faster if the … Read more
The error speaks for itself, in order to reference a composite primary key, you need a composite foreign key. (The composite primary key states that you need an unique combination of 2 fields to make a key – then you can’t possibly reference a unique key with just 1 column.) As to how this is … Read more
There is a way to bypass the validation and get it to work, thus indicating the column is a “@JoinColumnsOrFormulas” then put the solution: Error: @ManyToOne @JoinColumns(value = { @JoinColumn(name = “country_code”, referencedColumnName = “country_code”), @JoinColumn(name = “zip_code”, referencedColumnName = “code”)}) private Zip zip = null; @ManyToOne @JoinColumns(value = { @JoinColumn(name = “country_code”, referencedColumnName = … Read more
You can’t have MySQL do this for you automatically for InnoDB tables – you would need to use a trigger or procedure, or user another DB engine such as MyISAM. Auto incrementing can only be done for a single primary key. Something like the following should work DELIMITER $$ CREATE TRIGGER xxx BEFORE INSERT ON … Read more
This function should do the job. function groupByPartAndType($input) { $output = Array(); foreach($input as $value) { $output_element = &$output[$value[‘part’] . “_” . $value[‘type’]]; $output_element[‘part’] = $value[‘part’]; $output_element[‘type’] = $value[‘type’]; !isset($output_element[‘count’]) && $output_element[‘count’] = 0; $output_element[‘count’] += $value[‘count’]; } return array_values($output); } If both databases are on the same database server you would be able to … Read more
Hibernate needs to be able to compare and serialize identifiers. So the identifier class must be serializable, and override hashCode() and equals() consistently with the database’s notion of composite key equality. If you have a composite id mapped as properties of the entity, the entity itself is the identifier. A second approach is called a … Read more
You can mark both ActivityID and ActivityName properties with Key annotation or you can use fluent API as described by @taylonr. Edit: This should work – composite key defined with annotations requires explicit column order: public class ActivityType { [Key, Column(Order = 0)] public int ActivityID { get; set; } [Key, Column(Order = 1)] [Required(ErrorMessage … Read more
The Manning book Java Persistence with Hibernate has an example outlining how to do this in Section 7.2. Fortunately, even if you don’t own the book, you can see a source code example of this by downloading the JPA version of the Caveat Emptor sample project (direct link here) and examining the classes Category and … Read more
If Device table has composite primary key, then you need same composite foreign key on your NotificationMessageDevice table. How would SQL find Device without full primary key? Also you should make these fields to be part of NotificationMessageDevice table primary key. Otherwise you can’t guarantee primary key will be unique: public class NotificationMessageDevice { [Column(Order … Read more
You can use either fluent API: public class Category { public int CategoryId1 { get; set; } public int CategoryId2 { get; set; } public string Name { get; set; } public virtual ICollection<Product> Products { get; set; } } public class Product { public int ProductId { get; set; } public string Name { … Read more