Job offer letters issue

i am working on recruiting module in HCM Cloud i wanted to create Job offer letters. we have mulcible templates for same requisitions using some conditions in main template i wanted to call offer letters(sub template) please find the logic i am using below i wanted to use "is not null" or (!='') please help me to resolve this issue 

<?if:(LEGAL_EMPLOYER='LE' and BUSINESS_UNIT_NAME="BU" and NVL(ATTRIBUTE_NUMBER7,'N')!='N')?><?call-template:Generic_SS_Offer?><?END IF?>

<?if:(LEGAL_EMPLOYER='LE' and BUSINESS_UNIT_NAME="BU" and ATTRIBUTE_NUMBER7!='')?><?call-template:Generic_SS_Offer?><?END IF?>