AWK -F\| 'NR==FNR{n=int($2); a[n]=$2; next}
a[$1] Here am trying to understand it like this.
NR==FNR // file1==file2 

{

n=int($2);//n=53031-SC98 ;

a[n]=$2;//a[0]=53031-SC98 , a[1]=.....

next //??? here i dont understand

}

a[$1] // picking a[0] i.e 53031-SC98

{

print a[$1] FS $2 // printing .. O/P:: 53031-SC98 |Revenue - Cigarette Stamping

}