[SalesForce] Query Retention Email based on Data Extension in ExactTarget

The underscore (_) before the Data Extension name only applies to system-level 'Data Extensions' known as 'Data Views', such as _Subscribers, _Open, _Click, etc. For any of the Data Extensions you created in the account, you will only need the name of the Data Extension - no underscore required. Also, Data Extensions with spaces in their name should be surrounded by square brackets [ ].

With that in mind, your INNER JOIN is still a bit off. Since you are technically joining three tables (subscribers, usage, information), you will need two INNER JOINS: A -> B and B -> C. So it would look a bit more like:

FROM _subscribers a
INNER JOIN [UserData Usage] b
ON a.SubscriberKey = b.Subscriber Key
INNER JOIN
[Website Information] c
ON b.SubscriberKey = c.SubscriberKey

Lastly - relating multiple Data Extensions together through the data filters is possible when using Primary Keys and Data Relationships. Feel free to have a read through this:

https://help.marketingcloud.com/en/documentation/exacttarget/subscribers/data_extensions_and_data_relationships/data_relationships/

Lastly lastly, there aren't too many ExactTarget-specific SQL examples on this website, but I find just searching the regular Stack Exchange for general SQL help can get you through most problems.

Good luck!

You cannot use SET statements within Marketing Cloud, so your query above is not going to work. If your end goal is to unsubscribe these people from receiving marketing communications, then you are going to have to use a different approach.

Try something like this for your automation:

Step 1: Execute SQL Query to pull the email addresses you want to unsub from your SF data extension into a new data extension. Here is the query you would want to run for that:

SELECT EmailAddress, 'Unsubscribed' as Status FROM SF_DE WHERE some_criteria = whatever_value

Step 2: Execute Data Extract activity to extract that data extension's contents.

Step 3: Run File Transfer Activity to transfer that file name out of the Safehouse.

Step 4: Run Import Activity to import your file from the safehouse and into the All Subscribers list with an add/update data action in order to have these people be unsubscribed from receiving communications in SFMC.

Here are some relevant links for some background on these activities:

SQL Activity

Data Extension Extract Activity

File Transfer Activity

Import File Activity