How to write query to retrieve from two linked tables

Question

I need to retrieve user Id from module Relation table based on the user type which is in user table and they have relationship 

Please how to write that query in sql data source tag

<asp:SqlDataSource ID="SqlDataSource5" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
   SelectCommand="SELECT distinct [Full_Name], [UniID] FROM [Users] WHERE [UniID]= (SELECT [UniID]from [ModuleRelation]) AND [user_type]='Staff'"></asp:SqlDataSource>

Please help

thank you