SQLite database query for multiple tables using where for windows phone

Trying to develop a Windows phone 8.0 Store App.I need to retrieve records from a sqlite database which are having two tables so far i did not found any tutorial for it .here is what i am doing for get data from one table

 var existingconact = dbConn.Query<MainDB>("select * from MainDB where Id =1" ).FirstOrDefault(); 

but i want to achieve this to get data from two tables

var existingconact = dbConn.Query<MainDB>("SELECT MobcastMain.ID, MobcastMain.Name, health.age, FROM  MObcastMain CROSS JOIN health where Id =1" ).FirstOrDefault(); 

so how to do this and than how to fetch Data from it