User

id he unique ID of the identify call itself received_at When the page or screen call was received sent_at When the page or screen call was triggered by the user | Each trait of the user you record is created as it’s own column, and the column type is automatically inferred from your data. For example, you might have columns like email and first_name. |Example:

number of unique users by each day:

SELECT DATE(sent_at) AS Day, COUNT(DISTINCT(user_id)) AS Users
FROM <source>.identifies
GROUP BY day
ORDER BY day

Documentation / Reference

https://segment.com/docs/guides/how-to-guides/best-practices-identify/
http://support.kissmetrics.com/article/show/26403-identities
http://support.kissmetrics.com/article/show/understanding-identities