Webm.ag has a rundown of a few different GUI apps for administration/querying MySQL databases. Outside of the fact that they list HeidiSQL as a Linux app (it’s currently Win32 only, although in the comment exchange I had with the author, it apparently works well under Wine) its a decent list.
I have been using HeidiSQL regularly and generally liked it. On Linux, I still either go via a terminal (Konsole) or the staid but utile MySQL Query Browser.