What mysql database tables and relationships would support a Q&A survey with conditional questions? [closed]

Survey Database Design

Last Update: 5/3/2015
Diagram and SQL files now available at https://github.com/durrantm/survey

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This is a real classic, done by thousands. They always seems 'fairly simple' to start with but to be good it's actually pretty complex. To do this in Rails I would use the model shown in the attached diagram. I'm sure it seems way over complicated for some, but once you've built a few of these, over the years, you realize that most of the design decisions are very classic patterns, best addressed by a dynamic flexible data structure at the outset.
More details below:

Table details for key tables

answers

The answers table is critical as it captures the actual responses by users. You'll notice that answers links to question_options, not questions. This is intentional.

input_types

input_types are the types of questions. Each question can only be of 1 type, e.g. all radio dials, all text field(s), etc. Use additional questions for when there are (say) 5 radio-dials and 1 check box for an "include?" option or some such combination. Label the two questions in the users view as one but internally have two questions, one for the radio-dials, one for the check box. The checkbox will have a group of 1 in this case.

option_groups

option_groups and option_choices let you build 'common' groups. One example, in a real estate application there might be the question 'How old is the property?'. The answers might be desired in the ranges: 1-5 6-10 10-25 25-100 100+

Then, for example, if there is a question about the adjoining property age, then the survey will want to 'reuse' the above ranges, so that same option_group and options get used.

units_of_measure

units_of_measure is as it sounds. Whether it's inches, cups, pixels, bricks or whatever, you can define it once here.

FYI: Although generic in nature, one can create an application on top of this, and this schema is well-suited to the Ruby On Rails framework with conventions such as "id" for the primary key for each table. Also the relationships are all simple one_to_many's with no many_to_many or has_many throughs needed. I would probably add has_many :throughs and/or :delegates though to get things like survey_name from an individual answer easily without.multiple.chaining.

You could also think about complex rules, and have a string based condition field in your Questions table, accepting/parsing any of these:

• A(1)=3
• ( (A(1)=3) and (A(2)=4) )
• A(3)>2
• (A(3)=1) and (A(17)!=2) and C(1)

Where A(x)=y means "Answer of question x is y" and C(x) means the condition of question x (default is true)...

The questions have an order field, and you would go through them one-by one, skipping questions where the condition is FALSE.

This should allow surveys of any complexity you want, your GUI could automatically create these in "Simple mode" and allow for and "Advanced mode" where a user can enter the equations directly.

one way is to add a table 'question requirements' with fields:

• question_id (link to the "which brand?" question)
• required_question_id (link to the "do you smoke?" question)
• required_answer_id (link to the "yes" answer)

In the application you check this table before you pose a certain question. With a seperate table, it's easy adding required answers (adding another row for the "sometimes" answer etc...)