     
     static let Name = Expression<String>("name")
     static let Age = Expression<Int>("age")
+    static let BFF = Relationship<Person?>("best_friend")
     
     static func buildTable(tableBuilder: TableBuilder) {
         tableBuilder.column(Name)
-        tableBuilder.column(Age)
+        tableBuilder.column(Age, defaultValue: 0)
+        tableBuilder.relationship(BFF, mappedFrom: self)
     }
 }
 

        Person.Name <- "Jill"
        ])
    
    let peopleWhoRanUpTheHill = try Person.fetchAll()
    
    let jackQuery = Person.query.filter(Person.Name == "Jack")
    let personWhoBrokeHisCrown = try Person.fetch(jackQuery)
    
    try Person.updateAll([Person.Age += 10])
    let grownups = try Person.fetchAll()
    
    
    try jill.delete()
    let lastManOnEarth = try Person.fetchAll()
    
    try Person.deleteAll()
    try Person.dropTable()
    
}

    
    try Person.createTable()
    
    var jack = try Person.new([
            Person.Age <- 10,
            Person.Name <- "Jack"
        ])
