AI engineering glossary · SQL databases
What is LAG (LAG and LEAD)?
LAG and LEAD (also called LAG, LEAD): Window functions that read a value from an earlier row (LAG) or a later row (LEAD) in the ordered partition, without a self join. They are used for changes between consecutive rows.
LAG and LEAD: an example
amount - LAG(amount) OVER (ORDER BY month) gives month-on-month change in sales.
Related terms
More SQL databases terms
- LEFT JOIN
- LIMIT and OFFSET
- Locking
- Many-to-many relationship
- Materialized view
- Migration
- MVCC
- N+1 query problem
Where you learn it
LAG and LEAD is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.