If you are installing MediaWiki with a MySQL (MariaDB in my case) installation listening to localhost through a named pipe, you're suggested to enter "127.0.0.1" as database server, which is wrong - you have to enter a single dot. This got me stuck for hours until I found the solution not on the MW docs but on https://meta.wikimedia.org/w/index.php?title=Using_Named_Pipes&oldid=16325116
Tested with MW 1.28.0, Apache 2.4.25, PHP 7.1.3, MariaDB 10.1.22 running on Win7/64 SP1.