sqlt-diagram: 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 CentOS possible default full paths are:

/usr/bin/sqlt-diagram - from package: perl-SQL-Translator

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/sqlt-diagram - from package: libsql-translator-perl

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

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