title: MySQL TIMESTAMPDIFF function doesn't return expected result
body: <pre><code>SELECT
    M.strMemID                                          AS 'Member ID',
    M.strMemLastname                                    AS 'Last Name',
    M.STRMEMFIRSTNAME                                   AS 'First Name',
    M.strMemMiddlename                                  AS 'Middle Name',
    TIMESTAMPDIFF(YEAR, m.dtmMemBirthday, CURRENT_DATE) AS 'Age'
  FROM TBLMEMBER M
  WHERE m.strMemID NOT IN (SELECT DISTINCT m.strmemid
                           FROM tblmember m, tblmemberministry mm, tblpositionmemberministry pmm
                           WHERE m.strMemID = mm.strMMMemID AND mm.strmemmincode = pmm.strpmmmemmincode AND (
                             pmm.strPMMCode = 'POS041' OR PMM.STRPMMCODE = 'POS009' OR PMM.STRPMMCODE = 'POS010' OR
                             PMM.STRPMMCODE = 'POS012' OR PMM.STRPMMCODE = 'POS017' OR PMM.STRPMMCODE = 'POS021' OR
                             PMM.STRPMMCODE = 'POS028' OR PMM.STRPMMCODE = 'POS031' OR PMM.STRPMMCODE = 'POS037' OR
                             PMM.STRPMMCODE = 'POS039') AND mm.dtmMMDateQuit IS NULL AND pmm.dtmpmmdateto IS NULL AND
                                 TIMESTAMPDIFF(YEAR, m.dtmMemBirthday, CURRENT_DATE) &gt; 30);
  </code></pre>
  
  <p>This is my code. Please ignore the confusing subquery. My objective is to display members with <code>age &gt; 30</code>. I'm using the <code>TIMESTAMPDIFF</code>. But this query returns as well as those with age under 30. Can anyone help me?</p>