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 yiidbQuery object.
• Execute a query method.

To build an yiidbQuery 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'';"
   $user = (new yiidbQuery())
      ->select([''id'', ''name'', ''email''])
      ->from(''user'')
      ->where([''name'' => ''User10''])
      ->one();
   var_dump($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() {
   $user = (new yiidbQuery())
      ->select([''id'', ''name'', ''email''])
      ->from(''user'')
      ->where(''name = :name'', ['':name'' => ''User11''])
      ->one();
   var_dump($user);
}

Following will be the output.

Example of Hash format

public function actionTestDb() {
   $user = (new yiidbQuery())
      ->select([''id'', ''name'', ''email''])
      ->from(''user'')
      ->where([
         ''name'' => ''User5'',
         ''email'' => ''[email protected]''
      ])
      ->one();
   var_dump($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 yiidbQuery
  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() {
   $users = (new yiidbQuery())
      ->select([''id'', ''name'', ''email''])
      ->from(''user'')
      ->where([''between'', ''id'', 5, 7])
      ->all();
   var_dump($users);
}

Following will be the output.

OrderBy() Function

The orderBy() function defines the ORDER BY fragment.

Example −

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

Following will be the output.

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

Example −

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

You can see the following output −

The yiidbQuery 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.