Combining rows of data - linux

Question

File.csv
1234,1
6789,1
I'm trying to transform the file above to the below output :
1234,1
6789,1
Looking to merge rows using array or loop

Answer 1

Could you please try following, written and tested with shown samples in GNU awk.
awk '
BEGIN{
FS=OFS=","
}
{
sub(/ +$/,"")
first=$1
sub(/^[^,]*,/,"")
arr[first]=(arr[first]?arr[first] OFS:"")$0
}
END{
for(i in arr){
print i,arr[i]
}
}' Input_file
Explanation: Adding detailed explanation for above solution:
awk ' ##Starting awk program from here.
BEGIN{ ##Starting BEGIN section from here.
FS=OFS="," ##Setting field separator and output field separator as , here.
}
{
sub(/ +$/,"") ##Substituting spaces coming at last of line with NULL OP samples have it.
first=$1 ##Setting $1 value to first variable here.
sub(/^[^,]*,/,"") ##Substituting everything till first , with NULL here.
arr[first]=(arr[first]?arr[first] OFS:"")$0 ##Creating array arr with index of first and keep on adding values to it.
}
END{ ##Starting END block of this awk program from here.
for(i in arr){ ##Traversing through arr here for all elements here.
print i,arr[i] ##Printing i and value of arr with index of i here.
}
}' Input_file ##Mentioning Input_file name here.

Answer 2

One way, using a perl one-liner:
$ perl -F, -lanE '
push #{$g{$F[0]}}, #F[1..$#F];
END { print join(",", $_, $g{$_}->#*) for (sort { $a <=> $b } keys %g) }
' input.csv
1234,1,5,No,4,1,Not Applicable,2,5,6,8,6,1,3
6789,1,5,No,4,1,Not Applicable,2,5,6,8,6,1,3
Splits lines on commas, and adds all the fields to arrays stored in a hash table using the first element as the key, and then prints out all the combined lines in sorted order.