Settings like database name, host, user and password can be obtained from the file typo3conf/localconf.php in the Typo3 install directory.

$typo_db_username = '';
$typo_db_password = '';
$typo_db_host = ''; 
$typo_db = '';

Typo3 uses “backend” and “frontend” users.

Frontend users are stored in the table fe_users, their groups in table fe_groups.

usergroup: contains comma separated list of uids from table fe_groups

$conf['auth']['mysql']['checkPass']   = "
  SELECT password as pass
  FROM fe_users, fe_groups
  where fe_users.username='%{user}'
    and fe_groups.title ='%{dgroup}'
    and ( fe_users.usergroup REGEXP CONCAT( ',', CONVERT(fe_groups.uid, CHAR), ',') 
      or fe_users.usergroup REGEXP CONCAT( '^', CONVERT(fe_groups.uid, CHAR), ',')
      or fe_users.usergroup REGEXP CONCAT( ',', CONVERT(fe_groups.uid, CHAR), '$')
      or fe_users.usergroup REGEXP CONCAT( '^', CONVERT(fe_groups.uid, CHAR), '$')
    )
";

$conf['auth']['mysql']['getUserInfo'] = "SELECT password AS pass, name, email AS mail
                                         FROM fe_users
                                         WHERE username = '%{user}'";

$conf['auth']['mysql']['getGroups']   = "
  SELECT fe_groups.title as `group`
  FROM fe_users, fe_groups
  where fe_users.username='test'
    and ( fe_users.usergroup REGEXP CONCAT( ',', CONVERT(fe_groups.uid, CHAR), ',')
      or fe_users.usergroup REGEXP CONCAT( '^', CONVERT(fe_groups.uid, CHAR), ',')
      or fe_users.usergroup REGEXP CONCAT( ',', CONVERT(fe_groups.uid, CHAR), '$')
      or fe_users.usergroup REGEXP CONCAT( '^', CONVERD(fe_groups.uid, CHAR), '$')
    )
";

CONCAT output may be in different charset-collate. This may help:

$conf['auth']['mysql']['checkPass'] = "

  SELECT password AS pass
  FROM fe_users, fe_groups
  WHERE fe_users.username='%{user}'
    AND fe_groups.title ='%{dgroup}'
    AND ( fe_users.usergroup REGEXP CAST( CONCAT( ',', CONVERT(fe_groups.uid, CHAR), ',') 
          AS CHAR CHARACTER SET latin1) COLLATE 'latin1_german1_ci'
      OR fe_users.usergroup REGEXP CAST( CONCAT( '^', CONVERT(fe_groups.uid, CHAR), ',') 
          AS CHAR CHARACTER SET latin1) COLLATE 'latin1_german1_ci'
      OR fe_users.usergroup REGEXP CAST( CONCAT( ',', CONVERT(fe_groups.uid, CHAR), '$') 
          AS CHAR CHARACTER SET latin1) COLLATE 'latin1_german1_ci'
      OR fe_users.usergroup REGEXP CAST( CONCAT( '^', CONVERT(fe_groups.uid, CHAR), '$') 
          AS CHAR CHARACTER SET latin1) COLLATE 'latin1_german1_ci'
    )

";

$conf['auth']['mysql']['getGroups']   = "
  SELECT fe_groups.title as `group`
  FROM fe_users, fe_groups
  where fe_users.username='%{user}'
    and ( fe_users.usergroup REGEXP CAST( CONCAT( ',', CONVERT(fe_groups.uid, CHAR), ',') 
          AS CHAR CHARACTER SET latin1) collate 'latin1_german1_ci'
      or fe_users.usergroup REGEXP CAST( CONCAT( '^', CONVERT(fe_groups.uid, CHAR), ',') 
          AS CHAR CHARACTER SET latin1) collate 'latin1_german1_ci'
      or fe_users.usergroup REGEXP CAST( CONCAT( ',', CONVERT(fe_groups.uid, CHAR), '$') 
          AS CHAR CHARACTER SET latin1) collate 'latin1_german1_ci'
      or fe_users.usergroup REGEXP CAST( CONCAT( '^', CONVERT(fe_groups.uid, CHAR), '$') 
          AS CHAR CHARACTER SET latin1) collate 'latin1_german1_ci'
    )
";