How to write a query if the variable is empty?

Question

Yii

How to correctly write a query using Yii::app()->db->createCommand() if the variable in the condition may be empty?

$sql = $db->createCommand()
                ->select('`id`, `sub_id`, `min_price`,
                ->from('table')
                ->where("sub_id=$sub_id")
                ->query();

Answer 1

$sql = $db->createCommand()
     ->select(['id', 'sub_id', 'min_price']),
    ->from('table');
if(!empty($sub_id)){
    $sql->where(['sub_id' => $sub_id]);
}
$sql->query();

Answer 2

Use filterWhere()

Answer 3

If the where method can accept an empty string, then so be it.
The void can be different.
If you have it empty, it's '', then you need to compare like this:
$sub_id !== ''
If null, then like this
!is_null($sub_id)

Answer 4

wouldn't it be easier like this:

$query = new \yii\db\Query();

$query->createCommand()->queryAll();