tracker-sparql: 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/tracker-sparql - from package: tracker-utils

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

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