get 2 days ago query in mysql

Use Interval

WHERE `timestamp`
    BETWEEN DATE_SUB(NOW(), INTERVAL 2 DAY)
    AND DATE_SUB(NOW(), INTERVAL 1 DAY)

WHERE timestamp BETWEEN 
        DATE_SUB(DATE(NOW()), INTERVAL 2 DAY)
         AND DATE_SUB(DATE(NOW()), INTERVAL 1 DAY) 

You can also try DATE_ADD with a minus interval ;)

WHERE timestamp BETWEEN 
        DATE_ADD(DATE(NOW()), INTERVAL -2 DAY)
         AND DATE_ADD(DATE(NOW()), INTERVAL -1 DAY)