Is it possible to group rows by a day stored within a timestamp?

I'm not sure if this is even within the scope of MySQL to be honest or if some php is necess开发者_StackOverflowary here to parse the data. But if it is... some kind of stored procedure is likely necessary.

I have a table that stores rows with a timestamp and an amount.

My query is dynamic and will be searching based on a user-provided date range. I would like to retrieve the SUM() of the amounts for each day in a table that are between the date range. including a 0 if there are no entries for a given day

Something to the effect of...

SELECT 
   CASE
     WHEN //there are entries present at a given date
       THEN SUM(amount)
     ELSE 0
   END AS amountTotal,
   //somehow select the day
   FROM  thisTableName T
   WHERE T.timeStamp BETWEEN '$start' AND '$end'
   GROUP BY //however I select the day

This is a two parter...

is there a way to select a section of a returned column? Like some kind of regex within mysql?

Is there a way to return the 0's for dates with no rows?

select * from thisTableName group by date(created_at);

In your case, it would be more like

SELECT id, count(id) as amountTotal
FROM thisTableName
WHERE timeStamp BETWEEN '$start' AND '$end'
GROUP BY DATE(timeStamp);

Your question is a duplicate so far: link.