LibreOffice Calc count the number of distinct occurrences

This question has been asked many times before. One way is to enter the following formula in B6 and then press Ctrl+Shift+Enter:

=SUM(1/COUNTIF(B2:B5,B2:B5))

Other solutions are described at:

• https://forum.openoffice.org/en/forum/viewtopic.php?f=9&t=47223
• https://superuser.com/questions/238656/openoffice-get-distinct-values-from-column
• https://askubuntu.com/questions/114732/different-values-in-one-column

I prefer using a database such as LibreOffice Base instead, with a simple query:

SELECT COUNT(DISTINCT Week_Number) FROM Weeks_Table;