diff --git a/erpnext/patches/v10_0/set_discount_amount.py b/erpnext/patches/v10_0/set_discount_amount.py
index 019d245..eb8bb2d 100644
--- a/erpnext/patches/v10_0/set_discount_amount.py
+++ b/erpnext/patches/v10_0/set_discount_amount.py
@@ -15,42 +15,20 @@
 	buying_doctypes = ["Purchase Order Item", "Purchase Invoice Item", "Purchase Receipt Item", "Supplier Quotation Item"]
 
 	for doctype in selling_doctypes:
-		values = frappe.db.sql('''
-			SELECT
-				discount_percentage, rate_with_margin, price_list_rate, name		
-			FROM
-				`tab%s`
-			WHERE
-				ifnull(discount_percentage, 0) > 0
-		''' % (doctype), as_dict=True)
-		calculate_discount(doctype, values)
-
-	for doctype in buying_doctypes:
-		values = frappe.db.sql('''
-			SELECT
-				discount_percentage, price_list_rate, name		
-			FROM
-				`tab%s`
-			WHERE
-				discount_percentage > 0
-		''' % (doctype), as_dict=True)
-		calculate_discount(doctype, values)
-
-def calculate_discount(doctype, values):
-	rate = None
-	if not values: return
-	for d in values:
-		if d.rate_with_margin and d.rate_with_margin > 0:
-			rate = d.rate_with_margin
-		else:
-			rate = d.price_list_rate
-
-		discount_value = rate * d.get('discount_percentage') / 100
 		frappe.db.sql('''
 			UPDATE
 				`tab%s`
 			SET
-				discount_amount = %s
+				discount_amount = if(rate_with_margin > 0, rate_with_margin, price_list_rate) * discount_percentage / 100
 			WHERE
-				name = '%s'
-		''' % (doctype, discount_value, d.get('name')))
+				discount_percentage > 0
+		''' % (doctype))
+	for doctype in buying_doctypes:
+		frappe.db.sql('''
+			UPDATE
+				`tab%s`
+			SET
+				discount_amount = price_list_rate * discount_percentage / 100
+			WHERE
+				discount_percentage > 0
+		''' % (doctype))
\ No newline at end of file