How to compare two different files and two different columns bash - bash

Question

file 1
Client ID,USER ID,DH SERV, ...
,abs,2022-04-24, ...
,btg,2022-04-24, ...
file 2
abs,124235235
dsg,262356527
If second columnt from first file = first column from the second file, then add second column from second file in the first column 1 file.
I need to get:
Client ID,USER ID,DH SERV, ...
124235235,abs,2022-04-24, ...
,btg,2022-04-24, ...
How can I do this?
That's my attempts, but i don't understand very much
#!/bin/bash
#awk -F, 'FNR==NR{a[$1]=$0;next} ($1 in a){print $2,a[$1]}' mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv wamfactory_6100.csv > test
#awk -F, 'NR==FNR{a[FNR]=$1; next} {$2 == a[FNR] ? a[FNR]","$0 : $0}' mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv wamfactory_6100.csv > test
#awk -F, 'NR==FNR{a[FNR]=$1; next} {$2 == a[FNR] ? a[FNR]","$0 : $0}' wamfactory_6100.csv mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv > test
#awk -F, '{print FILENAME, NR, FNR, a[FNR]=$2,"||", b[NR]=$1}' mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv wamfactory_6100.csv > test
#Work
#awk -F, 'NR==FNR{A[$2]; next}$1 in A' mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv wamfactory_6100.csv > test
#awk -F, 'NR==FNR{A[NR]=$1; next}($2 in A) {print A[NR]}' wamfactory_6100.csv mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv> test
#awk -F, 'NR==FNR{A[$2]=$2; next}$1 in A{print A[$2]}' mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv wamfactory_6100.csv > test
#awk -F, 'FNR==NR{A[$1]=$1; next}$2 in A{print A[$1]}' mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv wamfactory_6100.csv > test
awk -F, 'NR==FNR {arr[$1]=$2 $1; next}
{print arr[$1]","$0}
' wamfactory_6100.csv mgcom_Deloviye_Linii_RU_conve_2022-04-24.csv > test

Answer 1

$ awk 'BEGIN{FS=OFS=","} NR==FNR{a[$1]=$2; next} $2 in a{$1=a[$2]} 1' file2 file1
Client ID,USER ID,DH SERV, ...
124235235,abs,2022-04-24, ...
,btg,2022-04-24, ...

Answer 2

This should do the trick:
awk 'BEGIN{FS=OFS=","}NR==FNR{a[$1]=$2} NR!=FNR{if($2 in a){print a[$2],$2,$3,$4 }else{print $0}}' file2 file1
Client ID,USER ID,DH SERV, ...
124235235,abs,2022-04-24, ...
,btg,2022-04-24, ...

Answer 3

Just using bash's associative and indexed arrays:
f(){
# delimit input/output with comma not whitespace
local IFS=,
# treat m as an associative array
declare -A m
# initialize m from second file
while read -r k v; do
m[$k]=$v
done <"$2"
# process lines of the first file
while read -ra i; do
# get second column
k=${i[1]}
# attempt substitution
i[1]=${m[$k]:-$k}
# print the line (quoting forces interpolation of IFS)
echo "${i[*]}"
done <"$1"
}
f "file 1" "file 2"