CAML Query not working in SharePoint 2010

CAML query is really very helpful while working with SharePoint Server Object Model to query data from SharePoint list and libraries.But while working with Server Object Model I was facing one issue ,that my query was not working properly, as i was not getting expected result.I also debug the code and their was no error while debugging in query.Below is the SPQuery which was not working.

SPQuery getSubHeaderQuery = new SPQuery();

getSubHeaderQuery.Query = "<Query><Where> <Eq> <FieldRef Name='MainHeader'/> <ValueType='Lookup'>" + MainHeader + "</Value> </Eq></Where></Query>";




Solution:
After spending some time and struggling with above query , i got soloution and finally my query starts working.Solution is very simple ,just remove the <Query> </Query> tag from the query string  and it will work fine .


SPQuery getSubHeaderQuery = new SPQuery();
getSubHeaderQuery.Query = "<Where> <Eq> <FieldRef Name='MainHeader'/> <Value Type='Lookup'>" + MainHeader + "</Value> </Eq></Where>";