Shell Programming and Scripting

XYZ 1
XYZ 3
abc 1
abc 1
qwe 2
qwe 1
qwe 3

SELECT max(rowid) FROM tablename GROUP BY columnname

$ sort -u test.txt | awk '{a[$1]++;next}END{for(i in a){if(a[i]>=2){print i}}}'
XYZ
qwe

# awk '$2>2{print $1}' infile
XYZ
qwe

1,2
2,3
1,3
1,2,3
2,3,1

# awk '{x=",";a[$1]=a[$1]&&p!=$2?a[$1]x$2:$2;p=$2}END{for(i in a){if(length(a[i])!=1)print i,a[i]}}' file
XYZ 1,3
qwe 2,1,3