framework/db/Query.php
public function andWhere($condition, $params = [])
    {
        if ($this->where === null) {
            $this->where = $condition;
        } elseif (is_array($this->where) && isset($this->where[0]) && strcasecmp($this->where[0], 'and') === 0) {
            $this->where[] = $condition;
        } else {
            $this->where = ['and', $this->where, $condition];
        }
        $this->addParams($params);
        return $this;
    }
public function andWhere($condition, $params = [])
    {
        if ($this->where === null) {
            $this->where = $condition;
        } elseif (is_array($this->where) && isset($this->where[0]) && strcasecmp($this->where[0], 'and') === 0) {
            $this->where[] = $condition;
        } else {
            $this->where = ['and', $this->where, $condition];
        }
        $this->addParams($params);
        return $this;
    }
Adds an additional WHERE condition to the existing one.
The new condition and the existing one will be joined using the `AND` operator.
@param string|array|ExpressionInterface $condition the new WHERE condition. Please refer to [[where()]]
on how to specify this parameter.
@param array $params the parameters (name => value) to be bound to the query.
@return $this the query object itself
@see where()
@see orWhere()