There are manby things which are considered as basics in dot net nuke.When you are using host sql window from dnn then most definitely you will need to have ideas of basic sql statements to fetch info from db.Few of them are:-
Listing all tables from DataBase:-

SELECT * FROM information_schema.Tables

Get Stored procedure description and Structure:-

select * from information_schema.routines where routine_name = ‘Stored Procedure Name’

Querry to fetch all tables in a database:

select * from sysobjects where type=’u’

A SqlCommand object allows you to query and send commands to a data base. It has methods that are specialized for different commands. The ExecuteReader method returns a SqlDataReader object for viewing the results of a select query. For insert, update, and delete SQL commands, you use the ExecuteNonQuery method. If you only need a single aggregate value from a query, the ExecuteScalar is the best choice.

ADO.NET provides an API for accessing database systems according to the programs. ADO.NET was created for the .NET Framework and it can be said that they are next generation of Active Data Objects (ADO). The .NET Framework contains several namespaces and classes, which are devoted to database accesses. Microsoft has created separate namespaces that are [...]