Flagging sourse with PROC SQL

[troxad]

How can we flag the source of each observations after merging two datasets using PROC SQL? The flag variable should identify whether the observation belongs to both datasets or any of them.

[ballardw]

It may help to show an example of the approach you are using to "merge" the two sets currently so we can discuss approaches based on your apparent data.

[SASKiwi]

Why are you repeating this post word-for-word? https://communities.sas.com/t5/SAS-Programming/Flagging-sourse-with-PROC-SQL/m-p/884981#M349658

Did the replies not help? If so please explain further.