Merge two files based on a 3rd key file

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# 1  
Old 01-06-2011
Merge two files based on a 3rd key file

I want to merge the two files based on the key file's columns.

The key file:

The other 2 files are From_file & To_file -
The From_file:

The To_file:

The o/p file has to be created by matching the left column in the key file to the first column in the from_file and substituting the entire line from the from_file. Similarly for the right column in the key that of the first column in the to_file.

Hence the o/p would look something like this:

I came accross a link in this forum about the matching strings in 2 files......but I got really confused Smilie!! Please can someone suggest?

# 2  
Old 01-06-2011
Try this,

 awk -F"~" 'NR==FNR{a[$1]++;b[$2]++;next} {split($0,c,"|");if(a[c[1]]){printf $0"~";getline tmp < "to_file"; split(tmp,d,"|");if(b[d[1]]){print tmp}}}' key_file from_file

This User Gave Thanks to pravin27 For This Post:
# 3  
Old 01-06-2011
awk -F\| 'FILENAME=="from_file"{a[$1]=$0;next;}FILENAME=="to_file"{b[$1]=$0;next;}{FS="~";if(a[$1]) $1=a[$1];if(b[$2]) $2=b[$2];}1' OFS="~" from_file to_file key_file

Last edited by anurag.singh; 01-07-2011 at 08:43 AM..
# 4  
Old 01-06-2011
Small variation:
awk '{sub(/ *$/,x)} NR==FNR{A[$1]=$0;m++;next} NR-FNR==m{B[$1]=$0;next} {print A[$1],B[$2]}' FS=\| OFS=\~ fromfile tofile FS=\~ keyfile

This User Gave Thanks to Scrutinizer For This Post:
# 5  
Old 01-06-2011
@Scrutinizer, given that every keyfile entry has reference in from and to files. If so, null check if a[$1] and b[$2] can be removed from my post (Also FILENAME=="key_file" check is not needed).
# 6  
Old 01-06-2011
@anurag, there is almost no difference with your solution, that is why I called it a small variation. I removed the trailing spaces which seemed to be present in the input files through the sub statement and used a different way to vary field separators and determining the file.. I think the checks are not needed, since it will produce an empty reference, which is preferable IMO.
# 7  
Old 01-06-2011
Seems a bit fluffy if they have serious amounts of data. I suspect 3-4 sorts, 2 joins and 1 intermediate file would do it in bulk: sort two files, join them, possibly resort the result, sort the third file, join it and the result.

With the right SQL flat file tools, you can just do it as a three way join.
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