Mastering GUI Programming with Python

Updating existing rows

To update existing rows in a table, you use the UPDATE statement, like so:

UPDATE coffees SET roast_id = 4 WHERE id = 2;

The SET clause is followed by a list of value assignments for the fields you want to change, and the WHERE clause describes conditions that must be true if a particular row is to be updated. In this case, we're going to change the value of the roast_id column to 4 for the record where the id column is 2.

SQL uses a single equals sign for both assignment and equality operations. It does not ever use the double-equals sign that Python uses.

Update operations can also affect multiple records, like this:

UPDATE coffees SET roast_id = roast_id + 1    WHERE coffee_brand LIKE 'Strawbunks';

In this case, we're ...