Question: i have a table with all the students names and another table with student name and their enrollments in classes i want to show both students with their class names even if they are not enrolled in any classes i used union between the enrolled and not enrolled the only problem that the names are duplicated 

Student (student\_id, student\_name, major, level, age)
Enrolled (student\_id, class\_name, semester)

and here's the MySQL query:

select student\_name,class\_name from student natural join enrolled union select student\_name,null as class\_name from student group by student\_name;

Answer: 
Try this control it will fulfil your requirements

<https://github.com/mineschan/MZTimerLabel>
Change the `repeats` parameter of NSTimer to `YES`. And you won't have to create a timer again each time it's fired. When your counter reaches to 5, just `invalidate` your timer.