Thanks for your reply… actually i am learning SQL on codecademy…
and below is the lesson and its instruction
Daily Count 2
Great! Now that we can convert timestamps to dates, we can count the Orders Per Date. Generally, when we count all records in a table we run a query with the count function, as follows:
select count(1) from users;
This will treat all rows as a single group, and return one row in the result set - the total count.
To count orders by their dates, we’ll use the date and count functions and pair them with the group by clause. Together this will count the records in the table, grouped by date.
For example, to see the user records counted by the date created, we use the date and count functions and group by clause as follows:
select date(created_at), count(1) from users group by date(created_at)
Use the date and count functions and group by clause to count and group the orders by the dates they were ordered_at.
group by 1
order by 1;
We now have the daily order count!
The order by 1 and group by 1 statements are shortcuts for order by date(ordered_at) and group by date(ordered_at).
Thats the reason i got confuse, why we are using ‘count(1)’ and what exactly it calculates?
Thanks once again.