Joining two space-separated files based on matching values in two different columns

Question

I have tried various solutions given in this site for this kind of problem and none of these are helping me out.

I have two files (space-separated, contains columns). Both the files contain the same number of records as given in my examples below.

Let me call the columns as A, B, C ... (These are the column headers.)

File 1:

A  B  C  D
-----------
a1 b1 c1 d1
a2 b2 c2 d2
a3 b3 c3 d3
a4 b4 c4 d4
a5 b5 c5 d5

File 2:

E B  A  F
---------
1 b5 a5 f
2 b2 a2 f
1 a1 b1 f
1 a3 b3 f
2 a4 b4 f 

I want to produce the merged file:

A  B  C  D  E
-------------
a1 b1 c1 d1 1
a2 b2 c2 d2 2
a3 b3 c3 d3 1
a4 b4 c4 d4 2
a5 b5 c5 d5 1

Answer 1

Does this come close to what you need (some formatting still to be done...)?

awk 'NR == FNR {T[$2,$3] = T[$3,$2] = $1; next} {print $0, T[$1,$2]}' file2 file1
A  B  C  D E
----------- 
a1 b1 c1 d1 1
a2 b2 c2 d2 2
a3 b3 c3 d3 1
a4 b4 c4 d4 2
a5 b5 c5 d5 1

Answer 2

a tedious join solution: first join on file1 col 1 and file2 col2, then join on file1 col 1 and file2 col 3:

{ 
    join -11 -22 -o 0,1.2,1.3,1.4,2.1 <(sed '1,2d' file1 | sort -k1,1) <(sed '1,2d' file2 | sort -k2,2) 
    join -11 -23 -o 0,1.2,1.3,1.4,2.1 <(sed '1,2d' file1 | sort -k1,1) <(sed '1,2d' file2 | sort -k3,3) 
} | sort -k 1,1 

outputs

a1 b1 c1 d1 1
a2 b2 c2 d2 2
a3 b3 c3 d3 1
a4 b4 c4 d4 2
a5 b5 c5 d5 1