In the "SQL help" menu you will find documentation which will explain how to create and maintain SQL queries which is need in various parts of Balthzar Client. If you have any further questions about this please contact Delacroy.
There is also a separate form in the admin section where it is possible to edit / create SQL Queries. This is found via "Client" -> "Main menu" -> "Administration" -> "System settings" -> "Basic data" -> "SQL Query".