The SQL namespace is for the BladeLogic database only
So you can use this to execute SQL statements on the BladeLogic database for example (It returns the output in xml format)
blcli_execute Sql executeSqlCommand "select value from system_property where name = 'DatabaseVersion'"
I think what you want to do is use NSH to nexec the SQL command line utilities for the paticular database you want to query. e.g. sqlcmd