SQL Tickets sold – Last 30 Days – use Where or Having?

How many tickets were sold for each route and each day, for the routes sold in the last 30 days from current day?

SELECT COUNT(TICKET_ID) NUMBER_TICKETS, ROUTE_CODE, FLIGHT_DATE 
FROM TICKETS 
WHERE (DAYS(CURRENT DATE)- DAYS(FLIGHT_DATE))<=30
GROUP BY ROUTE_CODE, FLIGHT_DATE

Should this be WHERE or HAVING? I am not sure which way is correct?

>Solution :

You want it in the WHERE.

Here is the best way to understand this —

The WHERE clause is used before the GROUP BY

The HAVING clause is used after the GROUP BY

So — you want to group items in the last 30 days — that happens before the group.