Glossary · Data Analytics

What is Window Function?

A SQL function that calculates across related rows without collapsing them into one row.

In more detail

Used for rankings (ROW_NUMBER, RANK, DENSE_RANK), running totals (SUM() OVER) and comparisons with previous rows (LAG, LEAD). A favourite interview topic.

Example

Top 3 products by revenue in each category with DENSE_RANK() OVER (PARTITION BY category …).

Learn it properlySQL for Data Analysis: GROUP BY, JOINs and Window Functions13 min lesson · Data Analytics

Related terms

Full glossary

Data CleaningFixing or removing incorrect, duplicate, inconsistent and missing data so analysis can be trusted.DataFrame (pandas)A table of rows and columns in Python’s pandas library, used to clean, analyse and reshape data.KPI (Key Performance Indicator)A number that shows how well a business or team is doing against an important goal.Pivot TableA spreadsheet tool that summarises data — sums, counts, averages — grouped by categories, by dragging fields.SQL JOINA SQL operation that combines rows from two tables based on a related column.