I'm working on a project for a school and so far I have 91 tables on a single database. All tables are linked with each other.

Is it normal to have this many tables in one database?


Do i need to make multiple databases?

If I do make multiple databases how can I link them together?

  • 1
    This question would be much more useful if you gave an example - apart from the student table, the existence of which tables made you worry? Mar 31, 2016 at 11:58
  • 1
    91? Try 800. Depending what you do, 91 does not even cut the main tables in an application. SAP R3 has more than 10000 tables, IIRC.
    – TomTom
    Sep 16, 2018 at 15:09

2 Answers 2


For a few years, I contracted with large firms to come in and fix up databases in sad need of repair. The databases were broken in a variety of ways. 100 tables strikes me as the middle of the range. They ranged from a low of about 30 tables to a high of over 500 tables.

This was in a previous century, so things may have changed.

One thing that has certainly changed is databases embedded in a single application. Designing and building databases was so difficult that they just about had to be multipurpose to justify the effort and expense,


10K tables can be a performance problem -- Tables are implemented using OS files, and the OS gets sluggish with that many files (etc) in a directory.

91 smells like "over normalization". Do not normalize "continuous" values likes dates and floats. Doing so, leads to terrible performance whenever you need a 'range' query.

Usually it is wrong to have two tables with the same set of fields. Hence, it is probably wrong to have different tables for different departments. Ditto for "forms".

Usually it is wrong to have two tables in a 1:1 mapping. So "most of the tables are linked to the student and the teacher" worries me.

  • the forms are different in a sense that they have different kind of information and fields, and the linking is not 1:1 it's 1:m like I have a attendance table which is linked with the student, each student would have different attendance. Mar 28, 2015 at 17:22

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