# FAQ: Window Functions - LEAD

This community-built FAQ covers the “LEAD” exercise from the lesson “Window Functions”.

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This exercise can be found in the following Codecademy content:

## FAQs on the exercise LEAD

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Given that you can use LEAD or LAG to calculate changes to weekly streams and changes to chart position, in what instances would you typically use one over the other?

For example the following provide the same results:

Example 1:
LEAD(streams_millions, 1) OVER (
PARTITION BY artist
ORDER BY week
) - streams_millions AS ‘streams_millions_change’

Example 2:
streams_millions - LAG(streams_millions, 1, streams_millions) OVER (
PARTITION BY artist
ORDER BY week
) AS ‘streams_millions_change’

I am a beginner using Windows functions. In what situations would you use LEAD and in what situations would you use LAG?