What is the difference between $with and $joinWith in Yii2 and when to use them?

joinWith uses JOIN to include the relations in the original query while with does not.

To illustrate further, consider a class Post with a relation comments as follows:

class Post extends \yii\db\ActiveRecord {    ...    public function getComments() {        return $this->hasMany(Comment::className(), ['post_id' => 'id']);    }}

Using with the code below:

$post = Post::find()->with('comments');

results in the following sql queries:

SELECT `post`.* FROM `post`;SELECT `comment`.* FROM `comment` WHERE post_id IN (...)

Whereas the joinWith code below:

$post = Post::find()->joinWith('comments', true)

results in the queries:

SELECT `post`.* FROM post LEFT JOIN `comment` comments ON post.`id` = comments.`post_id`;SELECT `comment`.* FROM `comment` WHERE post_id IN (...);

As a result, when using joinWith you may order by/filter/group by the relation. You may have to disambiguate the column names yourself.

Reference: http://www.yiiframework.com/doc-2.0/guide-db-active-record.html#lazy-eager-loading

Difference between with and joinWith

Using with method results the following SQL queries

$users = User::find()->with('userGroup');SELECT * FROM `user`;SELECT * FROM `userGroup` WHERE userId = ...

... while using joinWithwill result in this SQL query

$users = User::find()->joinWith('userGroup', true)SELECT * FROM user LEFT JOIN `userGroup` userGroup ON user.`id` = userGroup.`userId`;

So I'am using joinWith when I need to filter or search data in the related tables.

Additional informations

The docu -> http://www.yiiframework.com/doc-2.0/guide-db-active-record.html#joining-with-relations will tell you this:

"When working with relational databases, a common task is to join multiple tables and apply various query conditions and parameters to the JOIN SQL statement. Instead of calling yii\db\ActiveQuery::join() explicitly to build up the JOIN query, you may reuse the existing relation definitions and call yii\db\ActiveQuery::joinWith() to achieve this goal."

Which means, you are able to handle joins, innerJoins, outerJoins and all the good related stuff in Yii2 by yourself now. Yii (not Yii2) only uses join instead without letting the user decide about type of join. Details about "Join's" -> its a SQL-Based thing. You can read about this here http://en.wikipedia.org/wiki/Join_(SQL)

Please note that in addition to above awesome answers that helped me figure out how to use joinWith(), that whenever you want to use joinWith() and you have ambiguous column names, Yii / ActiveRecord automagically seems to pick a random column, instead of what you're usually expecting (the leftmost table). It is best to specify the leftmost table in the SELECT clause, by specifying something like $query->select("post.*"). I was getting ids from some inner tables and they were getting used like they were from the leftmost table, until I figured this out.

Another point to note is that you can specify an an alias for the joinwith relation, so you could say something like:

$post->find()->joinWith(["user u"])->where(["u.id"=>$requestedUser->id])->select("post.*")->orderBy(["u.created_at"=>SORT_DESC]);