Need help to declare and use variables in ALM 11 SQL script

Dears,

I am not able to decalre and use variables while using the ALM reports in my SQL I have defined the variable as:

DECLARE
_NUMBER varchar(50) = '50220',
_PLAN_FOLD varchar(100) = 'RFC50220_Applicant_Replacement'

I am trying to use the variable in the where clause as:

.....

WHERE
/*INPUT - RFC NO*/
        "requirement".RQ_USER_TEMPLATE_01 = _NUMBER