Is it possible to make the following regex-es into one?

```
cat file.txt | \ 
sed 's/\tNULL\t/\t\\N\t/g' | \
sed 's/^NULL\t/\\N\t/g' | \
sed 's/\tNULL$/\t\\N/g' | \
sed 's/^NULL$/\\N/g'' 

```

Maybe another thing to add, this is going over billions of rows a month so performance is a consideration.

**Solutions benchmark**
Thank you all for the suggestions, `perl` run the fastest for me. In case you wondered:

```
[/tmp]$ time cat /tmp/result_w_null.txt > /dev/null
real    0m0.045s
user    0m0.000s
sys     0m0.042s
[/tmp]$ time cat /tmp/result_w_null.txt | sed 's/\<NULL\>/\\N/g' > /dev/null
real    0m5.843s
user    0m2.472s
sys     0m3.852s
[/tmp]$ time cat /tmp/result_w_null.txt | sed 's/\tNULL\t/\t\\N\t/g' | sed 's/^NULL\t/\\N\t/g' | sed 's/\tNULL$/\t\\N/g' | sed 's/^NULL$/\\N/g' > /dev/null
real    0m7.078s
user    0m7.148s
sys     0m4.963s

#Suggestions:
[/tmp]$ time cat /tmp/result_w_null.txt | awk -F'\t' -v OFS='\t' '{for (i=1;i<=NF;i++) if ($i=="NULL") $i="\\N"}1' > /dev/null
real    0m20.196s
user    0m14.876s
sys     0m7.145s
[/tmp]$ time cat /tmp/result_w_null.txt | awk -v RS='(^|[\t\n])NULL(\tNULL)*([\t\n]|$)' '{ gsub(/NULL/, "\\N", RT); ORS=RT} 1' > /dev/null
real    0m10.611s
user    0m8.743s
sys     0m3.754s
[/tmp]$ time cat /tmp/result_w_null.txt | sed -E ':a; s/(\t|^)NULL(\t|$)/\1\\N\2/g; ta' > /dev/null
real    0m9.673s
user    0m5.723s
sys     0m5.678s
[/tmp]$ time cat /tmp/result_w_null.txt | perl -pe 's/(?:\t|^)\KNULL(?=\t|$)/\\N/g' > /dev/null
real    0m4.452s
user    0m3.237s
sys     0m2.288s

```