lag

lag

Showcasing the lag Postgres function which is a part of Postgres' windowing support.

Specifically, I wanted to illustrate a query where each row needs to be compared to the row preceding it.

Instructions

Follow these instructions to explore the windowing feature in Postgres.

1. Start the Postgres server
   • Use whatever method you prefer: HomeBrew, Docker, etc. Depending on how you install it, the username and database name will differ so take care to adjust the psql commands accordingly.
2. Apply the schema:

   • psql -f snapshots-schema.ddl

3. Insert test data:

   • psql -f snapshots-data.sql

4. Try out the queries snapshots-explore.sql and learn about lag!

Reference

• Postgres official docs: "Window Functions" tutorial
• Postgres official docs: "Window Functions" reference