foo,5
foo,7
foo,9
boo,5
boo,10
boo,10

foo,5,7,9
boo,5,10

awk 'BEGIN{OFS=FS=","}!(($1,$2)in c){c[$1,$2]=1;r[$1]=r[$1] OFS $2}
            END{for(i in r){print i r[i]}}' file

perl -F, -lane '$first{$F[0]}->{$F[1]} = (); END { print join(",", $_, sort { $a <=> $b } keys %{ $first{$_} } ) for keys %first }' < inputfile

$ cat bla.txt
foo,5
foo,7
foo,9
boo,5
boo,10
boo,10

$ { buffer="";
  while read i ; do
    key="${i%,*}" ;
    if [[ "$key" == "$oldkey" ]] ; then
      idx="${i#*,}";
      if [[ ! "$idx" == "$oidx" ]] ; then
        buffer+=",$idx" ;
        oidx="$idx";
      fi ;
    else
      test -z $buffer || echo $buffer ;
      oldkey="$key" ;
      buffer="$i" ;
      oidx="${i#*,}" ;
    fi ;
  done ; echo $buffer ; } < bla.txt
foo,5,7,9
boo,5,10
$

$ cat bla.txt
foo,5
foo,7
foo,9
boo,5
boo,10
boo,10

$ qry="select c1, group_concat(c2) from bla.txt group by c1" ;
$ q -d, "$qry" | sed -r 's/(,[^,]*)1/1/g'
boo,5,10
foo,5,7,9

datamash -t ',' -s -g 1 unique 2 <infile

boo,10,5
foo,5,7,9

#get sorted, unique keyword list
cut -d, -f 1 file | sort -u |
while read keyword ; do
  #echo keyword and sorted, unique occurrences of values
  #for keyword as output
  echo $keyword,$(grep "^$keyword," file | cut -d, -f2 |
              sort -u | tr 'n' ',' | sed 's/,$//' )
  >> sorted_file
done

cut -d, -f 1 file | sort -u | while read keyword ; do echo $keyword,$(grep "^$keyword," file | cut -d, -f2 | sort -u | tr 'n' ',' | sed 's/,$//' )  >> sorted_file ; done