Sorting a field within relation

[thipages]

Hi,

lets have a table A which has a fk a_bId refrencing table B, B containg a field b_field
I want to retrieve all A records sorted by b_field.
$sortingString="b_field"; is not working (see $sortingString below).
How may I manage it?
Thank you

$mapperA= new \Maphper\Maphper(
    new \Maphper\DataSource\Database($pdo, 'A', 'id')
);
$mapperB= new \Maphper\Maphper(
    new \Maphper\DataSource\Database($pdo, 'B', 'id')
);
$mapperA->addRelation("b", new\Maphper\Relation\One($mapperB,"a_bId","id"));

$sortingString="what may I put here?";
foreach ($mapperA->sort($sortingString) as $A) {
  echo ($A->b->b_field.":".$A->name);
}

[ckrudelux]

This is not possible cuase Maphper isn't doing SQL Joins. What you can do is use usort to sort the output with your own sorting function.

usort($mapperA, function($a, $b){
    if ($a->b->b_field == $b->b->b_field) {
        return 0;
    }
    return ($a->b->b_field < $b->b->b_field) ? -1 : 1;
});
foreach ($mapperA as $A) {
  echo ($A->b->b_field.":".$A->name);
}

Not tested, but I think you will get the Idea.

[garrettw]

This is not possible cuase Maphper isn't doing SQL Joins.

I wonder if it should be - or is there some advantage to not doing that?

[TRPB]

The reason for not doing SQL joins is that Maphper is designed to map relationships between arbitrary sources, we don't want to assume that both ends of the relationship are the same SQL database. One end could be a databse and another a CSV or JSON file.

Only PDO is supported currently but you could still define a relationship between two different databases

[garrettw]

It would be great if it could detect when two of the same source are being used and thus make use of specific features supported by that source to accomplish relational data retrieval, which would enable things like this. I suppose the question is, what should be returned when a source-supported sort is not available? Maybe throw an error saying something like, "Sorting method not defined for the sources in use."?