Example AWK program to merge two CSV files that contain a common column/field value.
Usage:
gawk -f merge.awk parent.csv child.csv
Will merge data from child.csv with that in parent.csv, using the common URL values in each file.
The code is described in the following blog post:
https://alex-sansom.info/content/using-gawk-merge-two-csv-files-common-field-value