xcode - Aligning tableView in specific place of ViewController in Swift -

i trying place tableview in specific position in viewcontroller (from half of page bottom). anytime when trying use constrains tableview getting lost somewhere (even if add horizontal , vertical centre in container)

here image of storyboard in assistant editor , view controller scene main.storyboard view http://i61.tinypic.com/2vtsl5k.jpg

and here image after adding constrains img http://i57.tinypic.com/10pww0k.png

actually fixed in simplest way adding missing constrains.