Hiding error messages: sql query
That setting is stored in the variable table as a serialised PHP string (in the "error_level" var) - I wouldn't advise updating that table manually with SQL (although obviously you can if you need to).

Far better would be to install Drush, and use vset as part of your deployment process instead:

drush vset error_level '2'


The available options are:


0 => None
1 => Errors and warnings
2 => All messages