Patient
 - title
 - name
 - surname
 - hospital_code  --------+
                          |
Hospital                  |
 - code  -----------------+
 - name

<?php
class Patient extends \yii\db\ActiveRecord{
    //.....
    // relation
    public  function getHospital(){
        return @$this->hasOne(Hospital::className(), ['code' => 'hospital_code']);
    }
    // virtual attribute hospitalName
    public function getHospitalName(){
        return @$this->hospital->name;
    }
    // virtual attribute fullName
    public function getFullname(){
        return $this->title .$this->name. " " .$this->surname;
    }
    public function attributeLabels()
    {
        return [
            //..............ฟิวด์อื่นๆ
           'fullName' => Yii::t('app', 'ชื่อ-นามสกุล'),
           'hospitalName' => Yii::t('app', 'โรงพยาบาล'),
            //..............
        ];
    }

<?= GridView::widget([
    'dataProvider' => $dataProvider,
    'filterModel' => $searchModel,
    'columns' => [
        ['class' => 'yii\grid\SerialColumn'],
        'title',
        'name',
        'surname',
        //เรียกผ่าน relation โดยตรง
        'hospital.name',
        // เรียกผ่าน virtual attribute hospitalName
        'hospitalName',
        // เรียกผ่าน virtual attribute fullName
        'fullName'
    ],
]); ?>

<?php
class PatientSearch extends Patient {

public function search($params)
{
    $query = Patient::find();
    $query->joinWith(['hospital']);
    $dataProvider = new ActiveDataProvider([
        'query' => $query,
    ]);
    // สำหรับ coluumn hospitalName
    $dataProvider->sort->attributes['hospitalName'] = [
        'asc' => ['lib_hospital.name' => SORT_ASC],
        'desc' => ['lib_hospital.name' => SORT_DESC],
    ];
    // สำหรับ coluumn fullName
     $dataProvider->sort->attributes['fullName'] = [
        'asc' => ['name' => SORT_ASC, 'surname' => SORT_ASC],
        'desc' => ['name' => SORT_DESC, 'surname' => SORT_DESC],
        'label' => 'ชื่อ - นามสกุล',
        'default' => SORT_ASC
    ];
    //................
 }

<?php
class PatientSearch extends Patient
{
    public $hospitalName;
    public $fullName;
    public function rules()
    {
        return [
            // ..........
            ['hospitalName','fullName'], 'safe'],
        ];
    }
    public function search($params)
    {
       //..........
        $query->orFilterWhere(['like', 'patient.name', $this->fullName])
              ->orFilterWhere(['like', 'patient.surname', $this->fullName])
              ->orFilterWhere(['like', 'lib_hospital.name', $this->hospitalName]);
    }
    //.........
}
?>