sql: 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/sql - from package: parallel

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

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