PARTITION BY

Compute windows inside groups.

PARTITION BY

PARTITION BY divides the window into groups. Each group is computed separately.

SELECT name, category, price,
  RANK() OVER (PARTITION BY category ORDER BY price DESC) AS rk
FROM products;

Separate ranking per category.

name, category, price, RANK() OVER (PARTITION BY category … is selected from products. RANK() is a window function: it computes a value for each row over the window defined in OVER (…), without collapsing rows.

PARTITION BY — details

PARTITION BY does not collapse like GROUP BY. Each row gets its own group's result.

For example, OVER (PARTITION BY category ORDER BY price DESC) gives number 1 to the most expensive product in each category; numbering restarts in every category.

Exercise PARTITION BY

Rank within each category with RANK() OVER (PARTITION BY category ORDER BY price DESC).

Show example solution

SELECT name, category, price,
  RANK() OVER (PARTITION BY category ORDER BY price DESC) AS rk
FROM products;

Test yourself

Add PARTITION BY

RANK() OVER (____ category ORDER BY price DESC)

Show answer

RANK() OVER (PARTITION BY category ORDER BY price DESC)

PARTITION BY: match the terms

PARTITION BY

group
category

section
separate rank

within group
no collapse

preserves
What does PARTITION BY do?
- Splits rows into groups
- Deletes rows
- Sorts them
- Filters
Show answer

Splits rows into groups — PARTITION BY divides the window into groups.

Next lesson: Summary - Window functions

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies