auto-discovering-relationship.md

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Auto Discovering Relationship

The FieldAttribute has a parameter parentTable that is used to define the parent table of the field. This is used in the case of a foreign key.

Once this attribute is set, the Repository can auto-discover the relationship between the tables and generate the proper SQL with the relationship to retrieve the data.

How to use

You can use the parentTable parameter in the FieldAttribute to define the parent table of the field.

<?php
#[TableAttribute(tableName: 'table1')]
class Class1
{
    #[FieldAttribute(primaryKey: true)]
    public ?int $id;
}

#[TableAttribute(tableName: 'table2')]
class Class2
{
    #[FieldAttribute(primaryKey: true)]
    public ?int $id;

    #[FieldAttribute(fieldName: "id_table1", parentTable: "table1")]
    public ?int $idTable1;
}

$repository1 = new Repository($dbDriver, Class1::class);
$repository2 = new Repository($dbDriver, Class2::class);

This will automatically create the relationship between table1 and table2 through the ORM system's internal relationship registry.

Generating Queries with Relationships

To generate the SQL query with the relationship, you can use the ORM static class:

<?php
$query = ORM::getQueryInstance("table1", "table2");

The command above will return a query object with the appropriate join, equivalent to:

<?php
$query = Query::getInstance()
    ->table('table1')
    ->join('table2', 'table2.id_table1 = table1.id');

Queries with Multiple Tables

You can also create queries with multiple joined tables by passing more table names:

<?php
$query = ORM::getQueryInstance("table1", "table2", "table3");

The ORM will automatically discover the path to connect these tables if relationships have been defined.

Manual Relationship Definition

If you need to define relationships manually (without using attributes), you can use the addRelationship method:

<?php
ORM::addRelationship("table1", "table2", "id_table1", "id");

This defines a relationship where table2.id_table1 is a foreign key that references table1.id.

You can also use Mapper objects:

<?php
$mapper1 = new Mapper(Class1::class);
$mapper2 = new Mapper(Class2::class);

ORM::addRelationship($mapper1, $mapper2, "id_table1");

In this case, the primary key will be automatically determined from the first mapper.

Getting Relationship Information

You can get information about relationships between tables:

<?php
// Get relationship keys
$relationships = ORM::getRelationship("table1", "table2");

// Get detailed relationship data
$relationshipData = ORM::getRelationshipData("table1", "table2");

Return Value of getRelationship

The ORM::getRelationship() method returns an array of relationship keys that define the path between the specified tables. Each key in the array is a string formatted as "tableA,tableB" which identifies a specific relationship in the internal relationship registry.

For example, if you call:

$relationships = ORM::getRelationship("table1", "table2");

It might return something like:

["table1,table2"]

If there are multiple tables involved in a path (like when finding relationships between more distant tables), it would return all the relationship keys in the path, like:

["table1,intermediateTable", "intermediateTable,table2"]

These keys identify the relationships in the internal registry and are used to retrieve the actual relationship details.

Return Value of getRelationshipData

The ORM::getRelationshipData() method returns the actual detailed relationship information for the tables. It takes the keys returned by getRelationship() and retrieves the corresponding relationship data objects.

The method returns an array of relationship data objects, where each object contains:

• parent: The parent table name
• child: The child table name
• pk: The primary key in the parent table
• fk: The foreign key in the child table

For example:

$relationshipData = ORM::getRelationshipData("table1", "table2");

Might return:

[
    [
        "parent" => "table1",
        "child" => "table2",
        "pk" => "id",
        "fk" => "id_table1"
    ]
]

This detailed information is used internally when automatically constructing joins in queries between the tables.

Limitations

• This feature does not support multiple relationships between the same tables
• Primary keys with two or more fields are not fully supported for auto-relationship discovery