Question

I have a table with dated records. I want a query that will show the number of records for each date.

Not hard, just a GROUP BY, right? Sure.

But I want to also show days where there were NO records. In this case, I would need to left join against a one-column table of consecutive dates, since a GROUP BY isn’t going to show a date that doesn’t exist.

Is there a better way of doing this? Or do I have to create a populate a table of dates just so I can join against it?

Answer 1

It would probably be easiest to build out the dates table

For example, if you wanted all dates from Jan 1, 2009 to today you could do the following:

DECLARE @start  AS DATETIME,
        @end    AS DATETIME

SELECT  @start = '2009-01-01',
        @end   = getdate()

DECLARE @dates TABLE    (
                        dt  DATETIME
                        )

WHILE (@start < @end)
BEGIN
    INSERT  @dates
    SELECT  @start

    SELECT @start = DATEADD(day, 1, @start)
END

SELECT  *
FROM    @dates

@dates will have a record for each day from @start to @end.