Enable multiple groups for a survey

[AdamDarlow]

A survey could have multiple groups (or tags or keywords) and a participant could only do the study if they haven't accessed any survey with any of the listed groups.

[gideongoldin]

We need to evaluate how useful and complicated this will be for users.

[jeff-hughes]

This is definitely a feature that I would love to see, and had planned on suggesting. However, allowing multiple groups would require changes to the database structure. I think the easiest way would be as follows:

• One table for groups (id, name)
• One table for surveys (id, URL, name?)
• One table for worker IDs (existing surveyrequest table: requestID, workerID, surveyID, time)
• A join table to connect groups with surveys (surveyID, groupID)

The join table essentially just contains one row for each "connection", allowing the same surveyID to be listed multiple times, one row for each group the survey is a part of.

The major issue is that any changes to the database structure are going to break previous versions. Some sort of script to help users migrate their DB structure would be important. But I'm not sure of the best way to do this.

[jeffzemla]

I'm not sure it's necessary to restructure the database at all. My plan was simply to enter one row per group for every access request. This preserves all backward compatibility and minimizes any back-end changes.

[jeff-hughes]

Ahh, I see. So if I have 600 participants for a survey that is in three groups, now we are talking about 1800 rows? I agree that preserves backward compatibility, but it does result in a lot of duplicated information...