I consulted the great Oracle of Wikipedia and it revealed the following to me:
MySQL is a relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. MySQL is officially pronounced (My S-Q-L), but often pronounced (My SeQueL). It is named for original developer Michael Widenius's daughter My.
I pronounce it and always have pronounced it My S-Q-L.