Uniq -c sort by column?

Question

Can uniq -c only get the number of occurrences of column 2 and then sort it according the number of occurrence? Also, after sorting, I don't want to show the number of occurrences. How to do it?

Here is my example input:

111111111 40
222222222 50
333333333 60
111111111 40
222222222 60 
333333333 50

To Be:

222222222 50
222222222 60
333333333 50 
333333333 60
111111111 40

Answer 1

$ cat file 
111111111 40
222222222 50
333333333 60
111111111 40
222222222 60 
333333333 50
$ sort file | uniq -c | sort -n -t ' ' -k 1 | awk '{print $2" "$3}'
222222222 50
222222222 60
333333333 50
333333333 60
111111111 40
$

1. sort file | uniq -c sort file | uniq -c gives you 3 columns in order: num(occurences) col1 col2
2. then sort -n -t ' ' -k 1 sorts the piped input (numerically -n according to num(occurences)) that is delimited by space(specified by t switch) according to 2nd column/key( -k 2 )
3. then awk '{print $2" "$3}' just prints the 2nd and 3rd field removing the number of occurrences field.