You could do it with awk:

awk -F'\t' -v OFS='\t' 'NR==FNR{a[$1]=$2;next}{$2=$2 OFS a[$2]}1' file2 file1
1   KD  35  
2   LBJ 6
3   YAO 11
4   LBJ 6
5   YAO 11
6   MJ  23
7   MJ  23
8   YAO 11
9   KD  35

Another option is to use join command:

join -1 2 -2 1 -o 1.1 1.2 2.2 -t $'\t' <(sort -k2,2 file1) <(sort file2) | sort -n

Explanation:

• -1 2 -2 1 tells the join command to join the second field of the first with the first field of the second file
• -o 1.1 1.2 2.2 This specifies the order of the fields in the output. The number before the dot is the file number, the number after the dot is the field number of the file
• -t $'\t' specifies that the delimiter is the tab character
• <(sort -k2,2 file1) <(sort file2) sorts the files by the field to be joined. The join command requires that the files are sorted.
• | sort -n sorts the output file

You could do it with awk:

awk -F'\t' -v OFS='\t' 'NR==FNR{a[$1]=$2;next}{print $0, a[$2]}' file2 file1
1   KD  35  
2   LBJ 6
3   YAO 11
4   LBJ 6
5   YAO 11
6   MJ  23
7   MJ  23
8   YAO 11
9   KD  35

Another option is to use join command:

join -1 2 -2 1 -o 1.1 1.2 2.2 -t $'\t' <(sort -k2,2 file1) <(sort file2) | sort -n

Explanation:

• -1 2 -2 1 tells the join command to join the second field of the first with the first field of the second file
• -o 1.1 1.2 2.2 This specifies the order of the fields in the output. The number before the dot is the file number, the number after the dot is the field number of the file
• -t $'\t' specifies that the delimiter is the tab character
• <(sort -k2,2 file1) <(sort file2) sorts the files by the field to be joined. The join command requires that the files are sorted.
• | sort -n sorts the output file

You could do it with awk:

awk -F'\t' -v OFS='\t' 'NR==FNR{a[$1]=$2;next}{$2=$2 OFS a[$2]}1' file2 file1
1   KD  35  
2   LBJ 6
3   YAO 11
4   LBJ 6
5   YAO 11
6   MJ  23
7   MJ  23
8   YAO 11
9   KD  35

Another option is to use sort command:

join -1 2 -2 1 -o 1.1 1.2 2.2 -t $'\t' <(sort -k2,2 file1) <(sort file2) | sort -n

Explanation:

• -1 2 -2 1 tells the join command to join the second field of the first with the first field of the second file
• -o 1.1 1.2 2.2 This specifies the order of the fields in the output. The number before the dot is the file number, the number after the dot is the field number of the file
• -t $'\t' specifies that the delimiter is the tab character
• <(sort -k2,2 file1) <(sort file2) sorts the files by the field to be joined. The join command requires that the files are sorted.
• | sort -n sorts the output file

You could do it with awk:

awk -F'\t' -v OFS='\t' 'NR==FNR{a[$1]=$2;next}{$2=$2 OFS a[$2]}1' file2 file1
1   KD  35  
2   LBJ 6
3   YAO 11
4   LBJ 6
5   YAO 11
6   MJ  23
7   MJ  23
8   YAO 11
9   KD  35

Another option is to use join command:

join -1 2 -2 1 -o 1.1 1.2 2.2 -t $'\t' <(sort -k2,2 file1) <(sort file2) | sort -n

Explanation:

• -1 2 -2 1 tells the join command to join the second field of the first with the first field of the second file
• -o 1.1 1.2 2.2 This specifies the order of the fields in the output. The number before the dot is the file number, the number after the dot is the field number of the file
• -t $'\t' specifies that the delimiter is the tab character
• <(sort -k2,2 file1) <(sort file2) sorts the files by the field to be joined. The join command requires that the files are sorted.
• | sort -n sorts the output file