OverviewTeaching: 20 min
Exercises: 10 minQuestions
How can I save a query for future use?
How can I remove a saved query?Objectives
Learn how to save repeated queries as ‘Views’ and how to drop them.
Saving queries for future use
It is not uncommon to repeat the same operation more than once, for example for monitoring or reporting purposes. SQL comes with a very powerful mechanism to do this: views. Views are queries saved in the database. You query it as a (virtual) table that is populated every time you query it.
Creating a view from a query requires you to add
CREATE VIEW viewname AS
before the query itself. For example, if we want to save the query giving
the number of journals in a view, we can write:
CREATE VIEW journal_counts AS SELECT ISSNs, COUNT(*) FROM articles GROUP BY ISSNs;
Now, we will be able to access these results with a much shorter notation:
SELECT * FROM journal_counts;
Assuming we do not need this view anymore, we can remove it from the database almost as we would a table:
DROP VIEW journal_counts;
In DBBrowser for SQLite, you can also create a view from any query by omitting
CREATE VIEW viewname AS statement and instead, clicking the small Save
icon at the bottom of the Execute SQL tab and then clicking Save as view.
Whatever method you use to create a view, it will appear in the list of views
under the Database Structure tab.
CREATE VIEWquery that
articlestable with the
ISSNsand returns the
COUNTof article records grouped by the
CREATE VIEW journal_counts AS SELECT journals.Journal_Title, COUNT(*) FROM articles JOIN journals ON articles.ISSNs = journals.ISSNs GROUP BY Journal_Title ORDER BY COUNT(*) DESC
Saving queries as ‘Views’ allows you to save time and avoid repeating the same operation more than once.