mysql gruppering efter vecka

Om du lagrar the_date som heltal måste du först konvertera det till datetime med FROM_UNIXTIME funktion:

 SELECT SUM(`amount_sale`) as total 
FROM `sales` 
WHERE `payment_type` = 'Account' 
GROUP BY WEEK(FROM_UNIXTIME(`the_date`))  

UPPDATERA :
Du kanske också vill ange veckonummer,

SELECT CONCAT('Week ', WEEK(FROM_UNIXTIME(`the_date`))) as week_number,
SUM(`amount_sale`) as total 
FROM `sales` 
WHERE `payment_type` = 'Account' 
GROUP BY WEEK(FROM_UNIXTIME(`the_date`))