delete users and all its related records Is there a way I could run mysql query from the backend to delete all the users and its related records except master-login.

There are some modules that help to do it or a via drush command but I am trying to do this from the backend database.

I am not sure about the how all the tables are maps. instead of figure it out I am trying to get a quick help here.
No.

You can install the Delete All module which provides some command line Drush commands to remove all content and users safely.


  This module is used to delete all content and/or users from a site.
  This is mainly a developer tool, which can come in handy in several
  cases, listed below.
  
  The usual way to do this is to go to Administer -> Content then select
  all the nodes and delete them. This works if you have a handful of
  nodes only. If you have hundreds or thousands of nodes, then it is not
  a practical solution.
  
  Another option is to directly delete the nodes from the node table in
  the database. This does not work properly, since there are also
  comments, and many tables for add on modules that needs to be cleaned.
  
  
  This is a test site that the client was using for a period of time,
  and they must clean it up before starting with real data.
  You are
  testing something that creates a lot of nodes (e.g. aggregator), and
  want to do it over and over again.
  You created a site in the past and
  want to replicate it again, but with new content.
  
  
  Note that for nodes,
  comments and all additions to nodes that contributed modules may have
  added. For users, any additional module data will also be deleted.