mk-merge-mqd-results: 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/mk-merge-mqd-results - from package: maatkit

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

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