relational: command not found

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 Debian possible default full paths are:

/usr/bin/relational - from package: relational

You may install the required package with command apt-get install {package}

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