SELECT m1.avizate, m2.facturate, m3.retururi, m1.month
FROM (

SELECT count( 1 ) AS avizate, month( date_sent )
MONTH
FROM orders
GROUP BY month( date_sent )
)m1, (
SELECT count( 1 ) AS facturate, month( date_purchased )
MONTH
FROM orders
GROUP BY month( date_purchased )
)m2, (

SELECT count( 1 ) AS retururi, month(
date_return )
MONTH
FROM orders

GROUP BY month( date_return )
)m3
WHERE m1.month = m2.month