How to count events based on parsing date - GROUP BY issues - sql

Question

I am attempting to count how many FAILURE events occurred per day, and the events are stored in a MainEventTable with columns of EventDateTime, EventId, and EventStatus. I'm using SQL Server Management Studio 2016, and it didn't recognize the DATEFROMPARTS function. This is the code that I've put together so far:
SELECT
t.EventDate,
SUM(t.EventCount) AS EventCount
FROM (
SELECT
CAST(
(
CAST(
DATEPART(yyyy,s.EventDateTime)
AS VARCHAR(4)
) + '-' +
CAST(
DATEPART(mm,s.EventDateTime)
AS VARCHAR(2)
) + '-' +
CAST(
DATEPART(dd,s.EventDateTime)
AS VARCHAR(2)
)
) AS DATE
) AS EventDate,
Count(s.EventId) AS EventCount
FROM (
SELECT
EventDateTime,
EventId
FROM
MainEventTable WITH(NOLOCK)
WHERE EventDateTime > '2016-12-07 00:00:00'
AND EventStatus = 'FAILURE'
) AS s GROUP BY CAST(
(
CAST(
DATEPART(yyyy,s.EventDateTime)
AS VARCHAR(4)
) + '-' +
CAST(
DATEPART(mm,s.EventDateTime)
AS VARCHAR(2)
) + '-' +
CAST(
DATEPART(dd,s.EventDateTime)
AS VARCHAR(2)
)
) AS VARCHAR(10)
)
) AS t
GROUP BY t.EventDate;
UPDATE: (THANKS to #wrslphil and #PM_77-1 for assistance with my GROUP BY issues) I've fixed my GROUP BY issues above and found that this worked, although it was very clunky. #KeithL simplified it MUCH more below...

Answer 1

Not a lot to go on here, but the query definitely won't run if you have an item that isn't in the group by list or aggregated in your select clause
I would think that you probably need to do a sum of your count field... like so
SELECT
t.EventDate,
SUM(t.EventCount) as EventCount
FROM (
SELECT
CAST(
(
CAST(
DATEPART(yyyy,s.EventDateTime)
AS VARCHAR(4)
) +
CAST(
DATEPART(mm,s.EventDateTime)
AS VARCHAR(2)
) +
CAST(
DATEPART(dd,s.EventDateTime)
AS VARCHAR(2)
)
) AS DATE
) AS EventDate,
Count(s.EventId) As EventCount
FROM (
SELECT
EventDateTime,
EventId
FROM
MainEventTable WITH(NOLOCK)
WHERE EventDateTime > '2016-12-07 00:00:00'
AND EventStatus = 'FAILURE'
) AS s
) AS t
GROUP BY t.EventDate;
The query is still unlikely to run because you have the same issue in your inner query. I would probably just do the transformation of the date within an inner query and encapsulate it with a query containing a count and group by

Answer 2

select CAST(EventDateTime AS DATE),COUNT(*)
FROM MainEventTable
WHERE EventDateTime > '2016-12-07 00:00:00'
AND EventStatus = 'FAILURE'
GROUP BY CAST(EventDateTime AS DATE)

Answer 3

Your sub-query has the following structure:
SELECT field1, COUNT(field2)
FROM theTable
In the same select you use a "raw" field and aggregation (COUNT). You do not have GROUP BY clause.
You are confusing your SQL engine, since it's impossible to figure out what value of field1 should be picked.
If you intention was to count how many records with non-NULL value of field2 each value of field1 has then the code would be:
SELECT field1, COUNT(field2)
FROM theTable
GROUP BY field1