The Query schema of Collaborative Application Markup Language (CAML) is used in various ways within the context of Microsoft SharePoint Foundation to define queries against list data. CAML queries are also used to retrieve data from SharePoint lists. To perform a filter based on Person or User Group or a specific user id follow any of the below approach.
And know I want to tell you how to use it based on a SharePoint List Column named as “User ID” of type Person or Group. The following listing program that you can use based on functions :
 If you know the display name of the user
 If you know the User Id ( not the login id)
 If you would like to filter based on current user (logged in User )