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how to design a 500+questions survey?

  • iscar
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9 years 5 months ago #113563 by iscar
if i design a survey has 500questions, the mysql table column is 500.
is it a problem of mysql database design?
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9 years 4 months ago #113568 by holch
Replied by holch on topic how to design a 500+questions survey?
Actually there will be a lot more columns, depending on the question type. For example, each subquestion of a multiple answer question type will have it's own column, etc.

Usually the limit of the database engine is around 1000 columns, but this depends a little on your installation.

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  • iscar
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9 years 4 months ago #113570 by iscar
Replied by iscar on topic how to design a 500+questions survey?
is that the coding problem? my tech staff told me it's not a good database design.
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9 years 4 months ago #113572 by holch
Replied by holch on topic how to design a 500+questions survey?
I am not an expert, but for analysis purpose, I think it is the standard. Because one thing is to have the best database layout, but then you need to be able to export the results database. Some write all answers into one cell, which I find a very annoying habit and I think it is a lot better to have each answer it its own column.

As I said, I am not an expert. But if you tech staff has a genius idea for a better database design, I am quite sure that the developers will be happy to have a look at it...

But they need to keep in mind that the results database needs to be able to be exported to use them in programs like SPSS for analysis.

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9 years 4 months ago - 9 years 4 months ago #113574 by c_schmitz
Replied by c_schmitz on topic how to design a 500+questions survey?
A 'better' database design is always a matter of taste.

The current database design is targetted at speed and easy readability. Other forms will be able to store more columns but will lack both speed and readybility.

TBH, not many people put 400 questions into their survey - and we try to cater to the mainstream user, not the extremists ;)

Best regards

Carsten Schmitz
LimeSurvey project leader
Last edit: 9 years 4 months ago by c_schmitz.
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9 years 4 months ago #113577 by holch
Replied by holch on topic how to design a 500+questions survey?
And if you don't have many multiple choice questions and don't need timestamps, 500 questions should still fit, shouldn't they?

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9 years 4 months ago #113580 by c_schmitz
Replied by c_schmitz on topic how to design a 500+questions survey?
Yes, they should. Timestamps is not a issue. Multiple choice are.

Best regards

Carsten Schmitz
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9 years 4 months ago #113584 by holch
Replied by holch on topic how to design a 500+questions survey?
But if you have the timestamps you add another column per question, don't you? Which means 500 questions will have 1000 columns, even if not multiple choice, or are the timestamps coming from a different database table?

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9 years 4 months ago #113585 by c_schmitz
Replied by c_schmitz on topic how to design a 500+questions survey?
Time stamps are held in a 2nd table - not in the responses table.

Best regards

Carsten Schmitz
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  • iscar
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9 years 4 months ago #113587 by iscar
Replied by iscar on topic how to design a 500+questions survey?
yes, my tech staff said if the the column is more than 500, best way is to split mysql table into 2 parts, it's better perfomance to read and insert.
i am not the mysql expert. i just think it's very common to creat a survey with more than 500 questions, because we have EM to jump to a question.
i also notice LS put all surveys questions into 1 table.i think it's better to put 1survey questions into 1 table.
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9 years 4 months ago #113591 by holch
Replied by holch on topic how to design a 500+questions survey?
One table one question? I don't think that makes much sense. You will bloat your database a lot.

And to be honest, I agree with Carsten, 500 questions is really a lot. I guess it is not for market research. Because from my experience, when the questionnaire gets too long, the last questions are actually not worth asking, because no one thinks about the question anymore, but just tries to click through. If they don't drop out.

Anyway. I agree that it would be a great addition if we could have a feature where Limesurvey could add a second table so that more questions can be included. When you have a lot of multipe response questions with a lot of answers, you get to the limit quite quickly.

Maybe you can make a feature request in the bug tracker?

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9 years 4 months ago #113664 by Mazi
Replied by Mazi on topic how to design a 500+questions survey?

holch wrote: Anyway. I agree that it would be a great addition if we could have a feature where Limesurvey could add a second table so that more questions can be included. When you have a lot of multipe response questions with a lot of answers, you get to the limit quite quickly.

Maybe you can make a feature request in the bug tracker?

We are aware of that problem and have tried to solve it in the past several times. BUT... this requires a major code rewrite and currently we do not have the resources for that.
We prefer to use our limited resources for several minor improvements instead of spending lots of time on a single feature only with the risk of leaving something unfinished at the end of developers leave or the like.

Anyway, this is on our list and maybe we participate at "Google Summer of Code" next year which would be an option for implementing such a major feature.

Until then you need to split up surveys and pass IDs to hidden questions to merge data later.
...or just don't annoy your users with hundreds of questions :-)

Best regards/Beste Grüße,
Dr. Marcel Minke
Need Help? We offer professional Limesurvey support: survey-consulting.com
Contact: marcel.minke(at)survey-consulting.com
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