Removing duplicates with DISTINCT

Which cities do our customers come from? If you select the city column from customers, a city with 500 customers shows up 500 times. DISTINCT fixes that.

Without DISTINCT:

SELECT city FROM customers;

You get one row per customer, repeats included.

With DISTINCT:

SELECT DISTINCT city FROM customers;

Now each city appears once. The database removes the repeats from your result only. The table itself doesn’t change.

With more than one column, DISTINCT looks at the combination:

SELECT DISTINCT city, name FROM customers;

This keeps every unique pairing of city and name, so a city can still appear more than once.

DISTINCT is useful for exploring a table you don’t know. It quickly shows which values a column really contains, including typos such as Hyderabad and Hyderbad appearing as separate entries.

Go deeper: SQLite SELECT reference