Question: I have a table to register which departments a person has worked and the date when it begin and ended.

If I define a period, how can I get for each person the number of days that he/she worked?

For example.

When the period is between 01/05/2014 and 31/07/2014 (date format is dd/mm/yyyy)

```
(id_department, id_person, date_start, date_end)

Person #856

190 856 04/07/2014  null
12  856 17/05/2004  13/06/2008
6   856 13/06/2008  19/09/2013
169 856 19/09/2013  03/07/2014

```

Should return number of days worked: 90 days (63 from 01/05/2014 to 07/07/2014 plus 27 from 04/07/2014 to 31/07/2014)

```
Person #900

19 900  30/07/2014  null
days: 1

Person #800

21 800  19/02/2013  05/06/2014
days: 35

Person #100

21 100  24/03/2012  05/05/2014
days: 4

```

and any combination of dates possible. Is it possible to get the sum in one query?

Answer: 
At the beginning an option is Change each image Universal to Specific, select retina 4 inches and then select Universal again.

But the best option is remove the derive data folder, go to:

Preferences -> Location -> Derive data folder and remove the folder with your project.

Then build and that works for me.

Happy to share this with you :)
I think it's a bug in Xcode (6.0.1) - take a look at your.xcassets/\*/Contents.json - there is nothing about @3x. I just added all the necessary stuff to my .appiconset by hand in json according to [the documentation](https://developer.apple.com/library/ios/documentation/userexperience/conceptual/mobilehig/IconMatrix.html#//apple_ref/doc/uid/TP40006556-CH27-SW1) you can check it on [my gist](https://gist.github.com/Czajnikowski/daf31d9f84e34e267671)