LIMIT, OFFSET, and DISTINCT

Taking just the top of the list

Real tables have millions of rows. You almost never want all of them. LIMIT n cuts the result off after n rows, and it combines beautifully with ORDER BY:

SELECT title, rating FROM movies
ORDER BY rating DESC
LIMIT 3;

Sort best-first, keep three: that is a top-3 query. Add OFFSET m to skip the first m rows before counting, which is how apps build page 2 of results: LIMIT 10 OFFSET 10 shows results 11 through 20.

An important habit: LIMIT without ORDER BY gives you some n rows, not the top n. Always sort before you cut.

Removing duplicates with DISTINCT

Ask for just the genre column and you get one value per row, duplicates included: scifi prints three times. SELECT DISTINCT collapses identical result rows into one:

SELECT DISTINCT genre FROM movies ORDER BY genre;

The next block runs the plain version first, then a divider, then the DISTINCT version so you can see the difference in one output.