In addition to adding new data, a common task is to update existing data, which can be done using an
UPDATE statement. Similar to the
INSERT statement, you have to specify exactly which table,
columns, and rows to update. In addition, the data you are updating has to match the data type of
the columns in the table schema.
UPDATE mytable SET column = value_or_expr, other_column = another_value_or_expr, … WHERE condition;
The statement works by taking multiple column/value pairs, and applying those changes to each and
every row that satisfies the constraint in the
Most people working with SQL will make mistakes updating data at one point or another. Whether it's
updating the wrong set of rows in a production database, or accidentally leaving out the
clause (which causes the update to apply to all rows), you need to be extra careful when
One helpful tip is to always write the constraint first and test it in a
SELECT query to make sure
you are updating the right rows, and only then writing the column/value pairs to update.
It looks like some of the information in our Movies database might be incorrect, so go ahead and fix them through the exercises below.