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Python GUI Programming with Tkinter
book

Python GUI Programming with Tkinter

by Alan D. Moore
May 2018
Beginner to intermediate content levelBeginner to intermediate
452 pages
11h 26m
English
Packt Publishing
Content preview from Python GUI Programming with Tkinter

Subqueries

Rather than using the raw primary key values of our instruments table each time, we can use a subquery as shown in the following SQL query:

UPDATE musicians SET main_instrument=(SELECT id FROM instruments WHERE name='guitar') WHERE name IN ('Robert Fripp', 'David Gilmour');

A subquery is a SQL query within a SQL query. If your subquery can be guaranteed to return a single value, it can be used anywhere you would use a literal value. In this case, we're letting our database do the work of figuring out what the primary key of guitar is, and inserting that for our main_instrument value.

In the WHERE clause, we've also used the IN operator to match against a list of values. This allows us to match against a list of values.

IN can be ...

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Publisher Resources

ISBN: 9781788835886Supplemental Content