Variables involving dates

Question

Hi,
Inside a query, I have a variable called @refdt1 whose value is set when we input a date in Query - Selection Criteria box.
declare @refdt1 date
set @refdt1 =
/* select @refdt1 from jdt1 t0 where t0.RefDate*/  '[%1]'
I want to create another variable called @refdt2 such that whatever date is input in Selection Criteria, @refdate2 should always give the end of the month.
For ex, if we input 01.05.11 (1 May 2011), @refdate2 should give 31.05.11 (31 May 2011) in same date format as @refdt1.
If we input 15.06.11 (15 Jun 2011), @refdate2 should give 30.06.11 (30 Jun 2011)
If we ignore the problem of February and leap years, then:
(a) MONTH(@refdt1) IN ('1', '3', '5', '7, '8', '10', '12' ) should give 31 as day
(b) MONTH(@refdt1) IN ('4', 6', '9', '11' ) should give 30 as day
Using concatenation and convert, I think we can build up @refdt2, but I don't know how to do it.
Grateful if anybody could show me how to write the code for @refdt2.
The code should be usable anywhere inside the query.
For ex, I could write:
WHERE T0.RefDate <= @refdt2
Thanks
Leon Lai

Answer 1

Hi,
I am making an effort to solve the problem using a particular field in a temporary table instead of a variable @refdt2.
I made this code. As illustration only, each code builds from the previous one, to see where the bug is.
declare @refdt1 date
set @refdt1 =
/*select 1 from jdt1 t0 where t0.RefDate*/  '[%1]'
CREATE TABLE #dates
(Col1 varchar(max),
Col2 int,
Col3 int,
Col4 varchar(max),
Col5 date)
INSERT INTO #dates VALUES
'31',
MONTH(@refdt1),
YEAR(@refdt1),
'31'   +  '/' +    cast (MONTH(@refdt1) as varchar )  +'/'   +
right( cast(   YEAR(@refdt1) as varchar) ,2),
CONVERT(DATE,('31'   +  '/' +    cast (MONTH(@refdt1) as varchar )  +'/'   + 
right( cast(  YEAR(@refdt1) as varchar) ,2)) , 103)
select * from #dates
The error lies in the code CONVERT(DATE ....
Error Msg:
Convert failed when converting date and/or time from character string
Can anyone help me correct that line - to convert the long string to a proper date?
Thanks
Leon