Show data from table even if there is no data!! Oracle

Question

I have a query which shows count of messages received based on dates. For Eg:

1 | 1-May-2012 
3 | 3-May-2012 
4 | 6-May-2012 
7 | 7-May-2012 
9 | 9-May-2012 
5 |         


        

Answer 1

You could achieve this with a left outer join IF you had another table to join to that contains all possible dates.

One option might be to generate the dates in a temp table and join that to your query.

Something like this might do the trick.

CREATE TABLE #TempA (Col1 DateTime)
DECLARE @start DATETIME = convert(datetime, convert(nvarchar(10), getdate(), 121))
SELECT @start

DECLARE @counter INT = 0

WHILE @counter < 50
BEGIN
    INSERT INTO #TempA (Col1) VALUES (@start)
    SET @start = DATEADD(DAY, 1, @start)
    SET @counter = @counter+1
END

That will create a TempTable to hold the dates... I've just generated 50 of them starting from today.

SELECT 
    a.Col1,
    COUNT(b.MessageID)
FROM
    TempA a
    LEFT OUTER JOIN YOUR_MESSAGE_TABLE b
        ON a.Col1 = b.DateColumn
GROUP BY
    a.Col1

Then you can left join your message counts to that.