How to Use Window Functions in MariaDB

Galaxy Glossary

How do I use window functions in MariaDB?

Window functions let you run aggregate-like calculations across related rows without collapsing them into a single result.

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What problem do MariaDB window functions solve?

Window functions return an aggregated value (sum, rank, moving average) for each row while keeping every row visible. They avoid self-joins and subqueries, making analytical queries shorter and faster.

How is the basic window function syntax structured?

Place the function in the SELECT list followed by OVER().Inside the parentheses you optionally define PARTITION BY, ORDER BY, frame clauses such as ROWS BETWEEN, or attach a named WINDOW.

When should I use `PARTITION BY`?

Use PARTITION BY when you need independent calculations per logical group, such as per customer or per order. Omitting it runs the calculation over the entire result set.

What is the difference between `ROWS` and `RANGE` frames?

ROWS counts physical rows before/after the current one, perfect for running totals.RANGE uses value ranges in the ORDER BY column, helpful for date buckets or price bands.

How do I create running totals of order amounts?

Order the rows by order_date and apply SUM(total_amount) OVER (PARTITION BY customer_id ORDER BY order_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW).

Can I combine multiple window functions in one query?

Yes.Each function can use its own window clause, or they can share a named window defined in the WINDOW clause at the end of the query.

Best practice: alias your windows

Define complex partitions once in a WINDOW w AS (...) clause, then refer to OVER w for every function. This keeps queries readable and reduces duplication.

How do window functions affect performance?

MariaDB materializes the window once per partition.Add appropriate indexes on PARTITION BY and ORDER BY columns to avoid full table scans.

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Why How to Use Window Functions in MariaDB is important

How to Use Window Functions in MariaDB Example Usage


-- Rank customers by lifetime spend
SELECT
    c.id,
    c.name,
    SUM(o.total_amount) AS lifetime_spend,
    RANK() OVER (
        ORDER BY SUM(o.total_amount) DESC
    ) AS spend_rank
FROM Customers AS c
JOIN Orders AS o ON o.customer_id = c.id
GROUP BY c.id, c.name;

How to Use Window Functions in MariaDB Syntax


SELECT
    column_list,
    aggregate_function() OVER (
        [PARTITION BY expr_list]
        [ORDER BY expr_list]
        [ROWS | RANGE frame_spec]
    ) AS alias
FROM table_name
[WINDOW win_name AS (PARTITION BY ... ORDER BY ... frame_spec)];

Example (running total per customer):

SELECT
    o.id,
    o.customer_id,
    o.order_date,
    o.total_amount,
    SUM(o.total_amount) OVER (
        PARTITION BY o.customer_id
        ORDER BY o.order_date
        ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    ) AS running_total
FROM Orders AS o;

Common Mistakes

Omitting ORDER BY in the window clause when the calculation depends on row order. Fix: always include ORDER BY for running totals or rankings.
Filtering with WHERE after using a window function that relies on unfiltered rows, which alters partitions. Fix: move filters into a subquery so the window sees the full data set.

Frequently Asked Questions (FAQs)

Are window functions slower than grouped aggregates?

Not necessarily. They avoid extra joins and let MariaDB process each partition once. With proper indexes, they can be comparable or faster.

Can I use window functions in UPDATE statements?

No. In MariaDB 10.5+, window functions are only allowed in SELECT clauses. Use a subquery to compute the windowed value, then join in an UPDATE.

Which MariaDB version introduced window functions?

Window functions became available in MariaDB 10.2.0 (stable in 10.2.2). Upgrade if you run an older release.

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