Hello,
I'm a MariaDB and MySQL packages maintainer.
My goal is to clean up the "Buildrequires:" for the "mysql-devel", "community-mysql-devel", "mariadb-devel" and "mariadb-connector-c-devel" though Fedora packages as a part of preparation for future changes in the stack.

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When to use which:
"BuildRequires: mariadb-connector-c-devel":
 - everywhere, where other two cases don't apply
 - this is the client library of MariaDB

"BuildRequires: mariadb-devel":
 - only when you *actually* need the server developement files - those are rare cases like building a server plugin
 - this requirement will pull in also the "mariadb-connector-c-devel", however it both clogs up your buildroot with unnecessary files
   and both makes harder for me to maintain the MariaDB / MySQL stack (sometimes a change appears which affect the whole stack)
 
"BuildRequires: community-mysql-devel":
 - only when you want to build *specifically* against "MySQL" - the DB from Oracle upstream - instead of MariaDB

"BuildRequires: mysql-devel":
 - never
 - currently, it will pull in the "mariadb-devel" package which will pull in the "mariadb-connector-c-devel" package
   However there are plans to remove it in a near future (which would likely make your package FTBFS)

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I've tested that your package builds in mock with the fix I propose.