Question:

this is table1

id1 Name ------------ 1 value1 2 value2

this is table2

id2 Name id1 --------------------- 1 value1 2 2 value2 1

this is table3

id3 Name id2 --------------------- 1 value1 2 2 value2 1

this is table4

id4 Name id3 --------------------- 1 value1 2 2 value2 1

I Want to join above 4 tables in <strong>Yii2 with model</strong>

select * from table1 left join table2 on table2.id2 = table1.id1 left join table3 on table2.id3 = table1.id2 left join table4 on table2.id4 = table1.id3

<strong>Step-1</strong> : Declaring Relations

To work with relational data using Active Record, you first need to declare relations in Active Record classes. The task is as simple as declaring a relation method for every interested relation, like the following,

class TableOneModel extends ActiveRecord { // ... public function getTableTwo() { return $this->hasMany(TableTwoModel::className(), ['id1' => 'id1']); } } class TableTwoModel extends ActiveRecord { // ... public function getTableThree() { return $this->hasMany(TableThreeModel::className(), ['id2' => 'id2']); } } ..... same create table3 and table4 relation

If a relation is declared with <a href="https://www.yiiframework.com/doc/api/2.0/yii-db-baseactiverecord#hasMany()-detail" rel="nofollow">hasMany()</a>, accessing this relation property will return an array of the related Active Record instances; if a relation is declared with <a href="https://www.yiiframework.com/doc/api/2.0/yii-db-baseactiverecord#hasOne()-detail" rel="nofollow">hasOne()</a>, accessing the relation property will return the related Active Record instance or null if no related data is found.

<strong>Step-2</strong> : Accessing Relational Data

After declaring relations, you can access relational data through relation names. This is just like accessing an object property defined by the relation method. For this reason, we call it relation property. For example,

$query = TableOneModel::find() ->joinWith(['tableTwo.tableThree']) ->all();

Refer <a href="https://www.yiiframework.com/doc/api/2.0/yii-db-activequery" rel="nofollow">yii\db\ActiveQuery</a>.

$query = (new \yii\db\Query()) ->from('table1 as tb1') ->leftJoin('table2 as tb2', 'tb1.id1 = tb2.id1') ->leftJoin('table3 as tb3', 'tb2.id2 = tb3.id2') ->leftJoin('table4 as tb4', 'tb3.id3 = tb4.id3') ->all();

Refer <a href="https://www.yiiframework.com/doc/guide/2.0/en/db-query-builder" rel="nofollow">Query Builder documentation</a> and <a href="https://www.yiiframework.com/doc/api/2.0/yii-db-query#leftJoin()-detail" rel="nofollow">leftJoin()</a>.

Use Gii to generate models, and if the foreign keys are defined well in the database, then the relations will be generated in your models. If not, then you can define the relations yourself. <a href="https://www.yiiframework.com/doc/guide/2.0/en/db-active-record#relational-data" rel="nofollow">See it here how to define those relations in a Yii2 model.</a><br /> Then you should be able to access an attribute of the model Table4 by doing this:

$table1 = Table1::findById(1); var_dump($table1->table2->table3->table4->attributes);