Date arithmetic in Cognos 8 - cognos

Question

What I need is a data item expression which outputs the starting date of the current quarter of last year. Finding the current year is easy, as is subtracting 1 year from that date. But beyond that I get stuck.
I currently have an ugly if expression for each quarter like:
if (extract(month,current_date) in (10,12,12))
then ((extract(year,_add_years (current_date,-1))||'-10-01'))
But no matter what I do I can't concatonate the year and date into string I can convert to a date object. The above code gives the error:
The operation "add" is invalid for the following combination of data types: "integer" and "character"
Trying to cast the integer as a character using cast() I get this error. I also get this error when trying to turn a character array into a date:
The operation "condexp" is invalid for the following combination of data types: "character" and "integer"
Trying to use SQL Server specific functions (it is a SQL Server database) just gives me an error that those functions are unavailable for local processing, so I can't seem to use SS date arithmatic, and I can't find anything particularly applicable in Cognos' built in date functions.
How can I manipulate a date to add a year to a known day/month combination and use that as a date object?

Answer 1

I'm using cognos 10.1.1, but it would work.
You can get the value by using the following code:
_make_timestamp(
extract(year, _add_years(current_date, -1)),
(floor((extract(month,current_date)-1)/3)*3+1),
01
)
The following is the simple way to get the starting month of the quarter.
(floor((extract(month,current_date)-1)/3)*3+1),
and you can convert timestamp to date or string.
cast(
_make_timestamp(
extract(year, _add_years(current_date, -1)),
(floor((extract(month,current_date)-1)/3)*3+1),
01
),
date
)
,
cast(
cast(
_make_timestamp(
extract(year, _add_years(current_date, -1)),
(floor((extract(month,current_date)-1)/3)*3+1),
01
),
date),
varchar(10)
)
plus, you can use extract function when you get a day value.
extract(day, _first_of_month (current_date))

Answer 2

I would go with SQLSERVER built-in functions tht exists in Cognos.
Here is an expression that works for me:
DATEADD({month},(3)*((DATEPART({quarter},[FullDateAlternateKey]))-1),
DATEADD({YEAR}, DATEDIFF({YEAR}, 0, dateadd({year},-1,[FullDateAlternateKey])), 0))
The FullDateAlternateKey field is my date field (from ADVERTUREWORKS DW DB).
If you still have problems, try to isolate the problem by trying this expression on new simple list report.