# Instantiation

First, instantiate a _QueryFactory_ with a database type:

```php
use Aura\SqlQuery\QueryFactory;

$queryFactory = new QueryFactory('sqlite');
```

You can then use the factory to create query objects:

```php
$select = $queryFactory->newSelect();
$insert = $queryFactory->newInsert();
$update = $queryFactory->newUpdate();
$delete = $queryFactory->newDelete();
```

Although you must specify a database type when instantiating a _QueryFactory_,
you can tell the factory to return "common" query objects instead of database-
specific ones.  This will make only the common query methods available, which
helps with writing database-portable applications. To do so, pass the constant
`QueryFactory::COMMON` as the second constructor parameter.

```php
use Aura\SqlQuery\QueryFactory;

// return Common, not SQLite-specific, query objects
$queryFactory = new QueryFactory('sqlite', QueryFactory::COMMON);
```

> N.b. You still need to pass a database type so that identifiers can be
> quoted appropriately.

All query objects implement the "Common" methods.

The query objects do not execute queries against a database. When you are done
building the query, you will need to pass it to a database connection of your
choice. In later examples, we will use [PDO](http://php.net/pdo) for the
database connection, but any database library that uses named placeholders and
bound values should work just as well (e.g. the [Aura.Sql][] _ExtendedPdo_
class).

[Aura.Sql]: https://github.com/auraphp/Aura.Sql