========================= FAQ: Databases and models ========================= .. _faq-see-raw-sql-queries: How can I see the raw SQL queries Django is running? ==================================================== Make sure your Django :setting:`DEBUG` setting is set to ``True``. Then do this:: >>> from django.db import connection >>> connection.queries [{'sql': 'SELECT polls_polls.id, polls_polls.question, polls_polls.pub_date FROM polls_polls', 'time': '0.002'}] ``connection.queries`` is only available if :setting:`DEBUG` is ``True``. It's a list of dictionaries in order of query execution. Each dictionary has the following:: ``sql`` -- The raw SQL statement ``time`` -- How long the statement took to execute, in seconds. ``connection.queries`` includes all SQL statements -- INSERTs, UPDATES, SELECTs, etc. Each time your app hits the database, the query will be recorded. If you are using :doc:`multiple databases`, you can use the same interface on each member of the ``connections`` dictionary:: >>> from django.db import connections >>> connections['my_db_alias'].queries If you need to clear the query list manually at any point in your functions, call ``reset_queries()``, like this:: from django.db import reset_queries reset_queries() Can I use Django with a pre-existing database? ============================================== Yes. See :doc:`Integrating with a legacy database `. If I make changes to a model, how do I update the database? =========================================================== Take a look at Django's support for :mod:`schema migrations `. If you don't mind clearing data, your project's ``manage.py`` utility has a :djadmin:`flush` option to reset the database to the state it was in immediately after :djadmin:`migrate` was executed. Do Django models support multiple-column primary keys? ====================================================== No. Only single-column primary keys are supported. But this isn't an issue in practice, because there's nothing stopping you from adding other constraints (using the ``unique_together`` model option or creating the constraint directly in your database), and enforcing the uniqueness at that level. Single-column primary keys are needed for things such as the admin interface to work; e.g., you need a single value to specify an object to edit or delete. Does Django support NoSQL databases? ==================================== NoSQL databases are not officially supported by Django itself. There are, however, a number of side projects and forks which allow NoSQL functionality in Django. You can take a look on `the wiki page`_ which discusses some projects. .. _the wiki page: https://code.djangoproject.com/wiki/NoSqlSupport How do I add database-specific options to my CREATE TABLE statements, such as specifying MyISAM as the table type? ================================================================================================================== We try to avoid adding special cases in the Django code to accommodate all the database-specific options such as table type, etc. If you'd like to use any of these options, create a migration with a :class:`~django.db.migrations.operations.RunSQL` operation that contains ``ALTER TABLE`` statements that do what you want to do. For example, if you're using MySQL and want your tables to use the MyISAM table type, use the following SQL:: ALTER TABLE myapp_mytable ENGINE=MyISAM;