is having millions of tables and millions of rows within them a common practice in MySQL database design?

Question

I am doing database design for an upcoming web app, and I was wondering from anybody profusely using mysql in their current web apps if this sort of design is efficient for

Answer 1

1 - Definitely not. Almost anyone you ask will tell you millions of tables is a terrible idea.

2 - Millions of ROWS is common, so just fine.

3 - Probably terribly, especially if the queries are written by someone who thinks it's OK to have millions of tables. That tells me this is someone who doesn't understand databases very well.

4 - See #3

5 - Impossible to tell. You will have a lot of extra overhead from the extra tables as they all need extra metadata. Space needed will depend on indexes and how wide the tables are, along with a lot of other factors.

In short, this is a very very very seriously bad idea and you should not do it.