[{"_id":101,"name":"ABC","students":[{"name":"john","age":10,"city":"CA"},{"name":"danial","age":15,"city":"KA"}]},{"_id":102,"name":"DEF","students":[{"name":"adam","age":20,"city":"NY"},{"name":"johnson","age":12,"city":"CA"}]}]

db.collection.find({"students.city":"CA"},{name:1,students:{$elemMatch:{"city":"CA"}}})