windows batch file combine csv in a folder by colu

Question

I would like to create a windows batch file to combine a folder full of CSV's into one CSV file but by column, not at the end.

file1.csv
A, B
1, 2
3, 4
5, 6

...

fileN.csv
C, D
1, 2
3, 4
5, 6

results.csv
A, B, C, D
1, 2, 1, 2
3, 4, 3, 4
5, 6, 5, 6

All of the examples I have seen combine 2 files with a defined name, or a simple copy one after the other. I cannot find how to copy by column!

Answer 1

I modified the solution I posted at merge-several-csv-file-side-by-side-using-batch-file topic in order to merge several files selected via a wild-card (instead of files given in the parameters). This solution can process a "variable number of files", but just a maximum of 8 files can be merged into another one; if there are more than 8 files, several "merged files" will be created with up to 8 files each in "mergedFiles" folder. If you want to generate one file from more than 8 files, you must repeat the process with the files in "mergedFiles" folder.

@echo off
setlocal EnableDelayedExpansion

rem MergeFiles2.bat: Merge several files horizontally, version 2
rem Antonio Perez Ayala

rem Get the list of files to merge into "file" array
set "num=0"
for %%a in (*.csv) do (
   set /A num+=1
   set "file[!num!]=%%a"
)

rem Merge files from the "file" array
set /A merge=0, last=0
if not exist mergedFiles\ md mergedFiles

:nextMerge
set /A merge+=1, first=last+1, last+=8
if %last% gtr %num% set last=%num%

rem Assemble the lists of redirections and SET /P commands for this merge
set "file1=!file[%first%]!"
echo/
echo The following files:
echo - %file1%
set /A first+=1
set "redirs="
set "commands="
set handle=2
for /L %%i in (%first%,1,%last%) do (
   echo - !file[%%i]!
   set /A handle+=1
   set "redirs=!redirs! !handle!<"!file[%%i]!" "
   set "commands=!commands! & set /P "line=^^!line^^!, " ^<^&!handle!"
)
if defined commands set "commands=!commands:~3!"
echo will be merged into:  mergedFiles\file%merge%.csv

rem First file in this merge is read with FOR /F command
rem The rest of files are read via standard handles, starting at # 3

%redirs% (
   for /F "usebackq delims=" %%a in ("%file1%") do (
      rem Get a line from first file
      set "line=%%a"
      rem Write-Read lines from all files, excepting the last one
      %commands%
      rem Write the line from last file
      echo !line!
   )
) > mergedFiles\file%merge%.csv

if %last% lss %num% goto nextMerge