Query Builder

Building on top of the foundations laid by DAO is Yii's Query Builder. Yii's Query Builder allows us to write database-agnostic queries in a programmatic way. Consequently, queries written through the Query Builder are significantly more readable than their DAO counterparts.

The basics of Query Builder involve the creation an instance of yii\db\Query, the construction of a statement, and then the execution of that query statement. For example, we could simply query for all the users in our database in Query Builder using the following code:

$users = (new \yii\db\Query())
    ->select(['id', 'email'])
    ->from('user')
    ->all();

Tip

When working with Query Builder, we're actually using the yii\db\Query class rather than yii\db\QueryBuilder. While yii\db\QueryBuilder can generate SQL statements similar to those generated by yii\db\Query, yii\db\Query enables these statements to be database-agnostic. In general, you'll...