This clause can only be used for select statements.
If you wish to filter duplicates based of those rows sharing a particular field
or set of fields, you may pass an array of fields to filter on. Beware that
this option might not be fully supported in all database systems.
### Examples:
Filters products with the same name and city
$query->select(['name', 'city'])->from('products')->distinct();
Filters products in the same city
$query->distinct(['city']);
$query->distinct('city');
Filter products with the same name
$query->distinct(['name'], true);
$query->distinct('name', true);
| public distinct ( array | Cake\Database\ExpressionInterface | string | boolean $on = [], boolean $overwrite = false ) | ||
| $on | array | Cake\Database\ExpressionInterface | string | boolean | Enable/disable distinct class or list of fields to be filtered on |
| $overwrite | boolean | whether to reset fields with passed list or not |
/**
* Tests that it is possible to select distinct rows
*
* @return void
*/
public function testSelectDistinct()
{
$query = new Query($this->connection);
$result = $query->select(['author_id'])->from(['a' => 'articles'])->execute();
$this->assertCount(3, $result);
$result = $query->distinct()->execute();
$this->assertCount(2, $result);
$result = $query->select(['id'])->distinct(false)->execute();
$this->assertCount(3, $result);
}
/**
* Returns the passed query after rewriting the DISTINCT clause, so that drivers
* that do not support the "ON" part can provide the actual way it should be done
*
* @param \Cake\Database\Query $query The query to be transformed
* @return \Cake\Database\Query
*/
protected function _transformDistinct($query)
{
if (is_array($query->clause('distinct'))) {
$query->group($query->clause('distinct'), true);
$query->distinct(false);
}
return $query;
}