i test other system, no question number limit.
compared to other system,can i creat 3000 questions in ls survey?
i know little about ls mysql structure.
as we set subquestion for each brand, the questions number should be at least 3000.

Does the other system specifically say that there is NO limit at all to the number of questions? Often they just say that from the system itself there is no limit. Later they often tell you: well, unfortunately the database doesn't support that many questions. I am not saying that this is the case, but it is good to ask this specifically.

I think 3000 questions will not be possible in Limesurvey, if you can't split your survey in 2 or 3 and join them via the endurl, especially if you have multiple choice questions. From what I know, the number of columns depends on the database engine.

Have a look here, this should explain things pretty well:
www.limesurvey.org/manual/General_FAQ#Ha...oftware_requirements

If you can't split the survey in 2 or 3, your maximum number will be somewhere around 1000 questions or even less (depending on whether you use a lot of multiple choice questions or matrix questions, which need one column per answer option!).

Maybe your solution would be to use PostgreSQL (see the link to the manual), which allows up to 1600 and there are options to increase that number. But I have no experience with that.

split the survey is not solution as EM is must to use.
about the database, only mysql, the best database, never use other database.
i checked other system, the mysql table is survey1001_1, survey1001_2...
the tables can added automatically.
can ls add mysql table automatically?

No, Limesurvey can currently not add mysql tables and from what I recall there was a discussion about this and it was pretty clear that this would mean a high additional programming effort and that the developers would rather implement new/other features than the possibility for extremely big surveys.

Given that e.g. a survey with 3000 questions is a pretty rare cases, I guess they would rather cater for the more common problems and think that the resources are better allocated elsewhere.

But 3000+ questions and a heavy use of EM will probably make Limesurvey quite slow anyway (just a guess, I have no proof nor experience with that).

There is always the option to sponsor such a feature, but I don't know what it would cost to implement something like that and the time this would take. Then one has to see how this compares to the costs of the other survey system that you are testing and if it is worth it.