Query Builder

Query builder allows you to create SQL queries in a programmatic way. Query builder helps you write more readable SQL-related code.

To use query builder, you should follow these steps −

• Build an yii\db\Query object.
• Execute a query method.

To build an yii\db\Query object, you should call different query builder functions to define different parts of an SQL query.

Step 1 − To show a typical usage of the query builder, modify the actionTestDb method this way.

public function actionTestDb() {
   //generates "SELECT id, name, email FROM user WHERE name = 'User10';"
   $user = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->where(['name' => 'User10'])
      ->one();
   var_dump($user);
}

Step 2 − Go to http://localhost:8080/index.php?r=site/test-db, you will see the following output.

Where() function

The where() function defines the WHERE fragment of a query. To specify a WHERE condition, you can use three formats.

• string format − ‘name = User10’
• hash format − [‘name’ => ‘User10′, ’email => [email protected]’]
• operator format − [‘like’, ‘name’, ‘User’]

Example of String format

public function actionTestDb() {
   $user = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->where('name = :name', [':name' => 'User11'])
      ->one();
   var_dump($user);
}

Following will be the output.

Example of Hash format

public function actionTestDb() {
   $user = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->where([
         'name' => 'User5',
         'email' => '[email protected]'
      ])
      ->one();
   var_dump($user);
}

Following will be the output.

Operator format allows you to define arbitrary conditions in the following format −

[operator, operand1, operand2]

The operator can be −

• and − [‘and’, ‘id = 1’, ‘id = 2’] will generate id = 1 AND id = 2 or: similar to the and operator
• between − [‘between’, ‘id’, 1, 15] will generate id BETWEEN 1 AND 15
• not between − similar to the between operator, but BETWEEN is replaced with NOT BETWEEN
• in − [‘in’, ‘id’, [5,10,15]] will generate id IN (5,10,15)
• not in − similar to the in operator, but IN is replaced with NOT IN
• like − [‘like’, ‘name’, ‘user’] will generate name LIKE ‘%user%’
• or like − similar to the like operator, but OR is used to split the LIKE predicates
• not like − similar to the like operator, but LIKE is replaced with NOT LIKE
• or not like − similar to the not like operator, but OR is used to concatenate the NOT LIKE predicates
• exists − requires one operand which must be an instance of the yii\db\Query class
• not exists − similar to the exists operator, but builds a NOT EXISTS (subquery) expression
• <, <=, >, >=, or any other DB operator: [‘<‘, ‘id’, 10] will generate id<10

Example of Operator format

public function actionTestDb() {
   $users = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->where(['between', 'id', 5, 7])
      ->all();
   var_dump($users);
}

Following will be the output.

OrderBy() Function

The orderBy() function defines the ORDER BY fragment.

Example −

public function actionTestDb() {
   $users = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->orderBy('name DESC')
      ->all();
   var_dump($users);
}

Following will be the output.

groupBy() Function

The groupBy() function defines the GROUP BY fragment, while the having() method specifies the HAVING fragment.

Example −

public function actionTestDb() {
   $users = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->groupBy('name')
      ->having('id < 5')
      ->all();
   var_dump($users);
}

Following will be the output.

The limit() and offset() methods defines the LIMIT and OFFSET fragments.

Example −

public function actionTestDb() {
   $users = (new \yii\db\Query())
      ->select(['id', 'name', 'email'])
      ->from('user')
      ->limit(5)
      ->offset(5)
      ->all();
   var_dump($users);
}

You can see the following output −

The yii\db\Query class provides a set of methods for different purposes −

• all() − Returns an array of rows of name-value pairs.
• one() − Returns the first row.
• column() − Returns the first column.
• scalar() − Returns a scalar value from the first row and first column of the result.
• exists() − Returns a value indicating whether the query contains any result
• count() Returns the result of a COUNT query
• other aggregation query methods − Includes sum($q), average($q), max($q), min($q). The $q parameter can be either a column name or a DB expression.