Display last 3 months from the entered date in SAP HANA

Hi All ,

I've a requirement to get the values for last 3 months from the month entered by the business through the Input parameter.

My Calmonth(Which is a string ) will be fetching data from the Input Parameter.

I've created 3 projections where each will take the value from input parameters and wanted to get month minus 1 , 2 and 3 respectively,but I'm not able to achieve it through this :

if((midstr("PERIOD",5,6) = midstr('$$INP_CALMONTH$$',5,6) - 1),"A",0)

and input parameter-1.

I've wrote both the above codes in Filter - Expression in a calculated view and it doesn't work .

The Calmonth format I've is : YYYYMM

Can anyone please help me in getting this ?

Regards,

Akhilesh