Nawaf,
Any direct SQL transactions to the CRM database are unsupported.
While the way to do it is same as working with SQL from a C# application, its not suggested way of working with CRM. CRM stores data of a single record in multiple tables and you might break the way it is done while working at SQL level. Also, you might
be aware that the database structure has changed in CRM 2013 and once you upgrade your system, there is a high probability that your SQL queries (specially Write) will fail.
HTH
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