The correct pronunciation as stated in the standard is "ess que ell". I can't quote the ISO standard because it doesn't seem to be freely available, but I'm quoting C. J. Date from his book SQL and Relational Theory:
In particular, I follow the standard in assuming the pronunciation "ess cue ell", not "sequel" (though this latter is common in the field), thereby saying things like an SQL table, not a SQL table. (page xvii)
In particular, I follow the standard in assuming the pronunciation "ess cue ell", not "sequel" (though this latter is common in the field), thereby saying things like an SQL table, not a SQL table. (page xvii)