awk replace field value based on matching value in another file

Question

I have 2 files, Zipcode.txt and Address.csv:

ZipCode.txt
12345
23456
34567
45678

Address.csv
12345,3587 main st,apt j1,city,new jersey
23456,4215 1st st. s.,suite a2,city,new jersey
65432,115 main st,,city,new jersey
45678,654 2nd st n.,city,new jersey

If the zipcode field in Zipcode.txt matches the zipcode field in Address.csv, I want to change the 4th field from city to found. Here's what I want:

12345,3587 main st,apt j1,found,new jersey
23456,4215 1st st. s.,suite a2,found,new jersey
65432,115 main st,,city,new jersey
45678,654 2nd st n.,found,new jersey

This is what I have tried:

awk -F',' 'BEGIN{OFS=FS}NR==FNR{a[$1]=1;next}a[$1]{$4="found"}1' Address.csv ZipCode.txt

Answer 1

This will search whether the zip code in the first field of Address.csv is found anywhere in Zipcode.txt:

awk -F, -v OFS="," 'NR==FNR {a[$1]++;next} $1 in a {$4="found"} 1' Zipcode.txt Address.csv

Output:

12345,3587 main st,apt j1,found,new jersey
23456,4215 1st st. s.,suite a2,found,new jersey
65432,115 main st,,city,new jersey
45678,654 2nd st n.,city,found

Note that the last line is not as expected, because city is not the fourth field in the input: a comma is likely missing in the last line of Address.csv.