How to use multiple primary keys

android, ormlite

Solution

Limitations

For simplicity, and to be able to have the same POCO class persisted in db4o, memcached, redis or on the filesystem (i.e. providers included in ServiceStack), each model must have a single primary key, by convention OrmLite expects it to be Id although you use [Alias("DbFieldName")] attribute it map it to a column with a different name or use the [PrimaryKey] attribute to tell OrmLite to use a different property for the primary key.

You can still SELECT from these tables, you will just be unable to make use of APIs that rely on it, e.g. Update or Delete where the filter is implied (i.e. not specified), all the APIs that end with ById, etc.

Workaround single Primary Key limitation

A potential workaround to support tables with multiple primary keys is to create an auto generated Id property that returns a unique value based on all the primary key fields, e.g:

public class OrderDetail
{
    public string Id { get { return this.OrderId + "/" + this.ProductId; } }

    

public int OrderId { get; set; }
    public int ProductId { get; set; }
    public decimal UnitPrice { get; set; }
    public short Quantity { get; set; }
    public double Discount { get; set; }
}

https://github.com/ServiceStack/ServiceStack.OrmLite/#limitations

Problem

I created database, for my android app, witch has 16 tables. I want to use ORMlite mapping. The problem is that I didn't find examples where you have composite id(Multiple primary keys). For example I have table: ``` CREATE TABLE IF NOT EXISTS `Tourist_Guide`.`Cultural_activity` ( `City_Id` INT NOT NULL , `activity_Id` INT NOT NULL , `Cultural_activity_Id` INT NOT NULL AUTO_INCREMENT , `Name_Of_Cultural_activity` VARCHAR(30) NOT NULL , PRIMARY KEY (`Cultural_activity_Id`, `City_Id`, `activity_Id`) , INDEX `fk_Cultural_activity_activity1` (`City_Id` ASC, `activity_Id` ASC) , CONSTRAINT `fk_Cultural_activity_activity1` FOREIGN KEY (`City_Id` , `activity_Id` ) REFERENCES `Tourist_Guide`.`activity` (`City_Id` , `activity_Id` ) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; ``` Can you, please, tell me how to map this table to class(how this class should look like), is that even possible?

Original source