pqxx-config: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/pqxx-config - from package: libpqxx-devel

You may install the required package with command yum install {package}
Error in other languages:
pqxx-config: bevel nie gevind nie
pqxx-config: comandă negăsită
pqxx-config: comando não encontrado
pqxx-config: commande introuvable
pqxx-config: command not found
pqxx-config: käsku ei ole
pqxx-config: không tìm thấy lệnh
pqxx-config: komanda nerasta
pqxx-config: Kommando nicht gefunden.
pqxx-config: kommandot finns inte
pqxx-config: komut yok
pqxx-config: nie znaleziono polecenia
pqxx-config: níor aimsíodh an t-ordú
pqxx-config: no se encontró la orden
pqxx-config: no s'ha trobat l'ordre
pqxx-config: opdracht niet gevonden
pqxx-config: parancs nem található
pqxx-config: perintah tidak ditemukan
pqxx-config: príkaz nenájdený
pqxx-config: příkaz nenalezen
pqxx-config: команда не найдена
pqxx-config: командата не е открита
pqxx-config: 命令找不到
pqxx-config: コマンドが見つかりません