mysql-schema-diff: 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 Debian possible default full paths are:

/usr/bin/mysql-schema-diff - from package: libmysql-diff-perl

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