MySQL 5.1 Reference Manual  /  ...  /  Limits on Number of Databases and Tables

C.7.2 Limits on Number of Databases and Tables

MySQL has no limit on the number of databases. The underlying file system may have a limit on the number of directories.

MySQL has no limit on the number of tables. The underlying file system may have a limit on the number of files that represent tables. Individual storage engines may impose engine-specific constraints. InnoDB permits up to 4 billion tables.


User Comments
  Posted by Rick James on March 14, 2015
A table involves one to three files in a directory. A database involves one directory in a parent directory. Having a "lot" of tables or databases can be slow. This is because the Operating System does not necessarily do a speedy job of locating files/directories when there are tens of thousands of such in a single directory.
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