refactor: updated sql query for item variants
diff --git a/erpnext/manufacturing/doctype/production_plan/production_plan.py b/erpnext/manufacturing/doctype/production_plan/production_plan.py
index 99b6926..efb2d92 100644
--- a/erpnext/manufacturing/doctype/production_plan/production_plan.py
+++ b/erpnext/manufacturing/doctype/production_plan/production_plan.py
@@ -116,21 +116,21 @@
 
 		so_list = self.get_so_mr_list("sales_order", "sales_orders")
 
-		item_condition = ""
+		item_condition = variant_of_bom = ""
 		if self.item_code:
 			if frappe.db.exists('Item', self.item_code):
-				is_variant = frappe.db.get_value('Item', self.item_code, ['variant_of'])
-			if is_variant:
-				variant_of = is_variant
+				has_variant_bom = frappe.db.exists({'doctype': 'BOM', 'item': self.item_code})
+				if not has_variant_bom:
+					variant_of_bom = "'%s'" % frappe.db.get_value('Item', self.item_code, ['variant_of'])
 			item_condition = ' and so_item.item_code = {0}'.format(frappe.db.escape(self.item_code))
-		
+
 		items = frappe.db.sql("""select distinct parent, item_code, warehouse,
 			(qty - work_order_qty) * conversion_factor as pending_qty, description, name
 			from `tabSales Order Item` so_item
 			where parent in (%s) and docstatus = 1 and qty > work_order_qty
-			and exists (select name from `tabBOM` bom where bom.item= "%s"
+			and exists (select name from `tabBOM` bom where bom.item= %s
 					and bom.is_active = 1) %s""" % \
-			(", ".join(["%s"] * len(so_list)), variant_of or "so_items.item_code", item_condition), tuple(so_list), as_dict=1)
+			(", ".join(["%s"] * len(so_list)), variant_of_bom or "so_item.item_code", item_condition), tuple(so_list), as_dict=1)
 			
 		if self.item_code:
 			item_condition = ' and so_item.item_code = {0}'.format(frappe.db.escape(self.item_code))
@@ -686,7 +686,7 @@
 		}
 
 def get_sales_orders(self):
-	so_filter = item_filter = ""
+	so_filter = item_filter = variant_of_bom = ""
 	if self.from_date:
 		so_filter += " and so.transaction_date >= %(from_date)s"
 	if self.to_date:
@@ -700,9 +700,9 @@
 
 	if self.item_code:
 		if frappe.db.exists('Item', self.item_code):
-			is_variant = frappe.db.get_value('Item', self.item_code, ['variant_of'])
-			if is_variant:
-				variant_of = is_variant
+			has_variant_bom = frappe.db.exists({'doctype': 'BOM', 'item': self.item_code})
+			if not has_variant_bom:
+				variant_of_bom = "'%s'" % frappe.db.get_value('Item', self.item_code, ['variant_of'])
 		item_filter += " and so_item.item_code = %(item)s"
 
 	open_so = frappe.db.sql("""
@@ -712,18 +712,17 @@
 			and so.docstatus = 1 and so.status not in ("Stopped", "Closed")
 			and so.company = %(company)s
 			and so_item.qty > so_item.work_order_qty {0} {1}
-			and (exists (select name from `tabBOM` bom where bom.item=%(item_code)s
+			and (exists (select name from `tabBOM` bom where bom.item= {2}
 					and bom.is_active = 1)
 				or exists (select name from `tabPacked Item` pi
 					where pi.parent = so.name and pi.parent_item = so_item.item_code
 						and exists (select name from `tabBOM` bom where bom.item=pi.item_code
 							and bom.is_active = 1)))
-		""".format(so_filter, item_filter), {
+		""".format(so_filter, item_filter, variant_of_bom or "so_item.item_code"), {
 			"from_date": self.from_date,
 			"to_date": self.to_date,
 			"customer": self.customer,
 			"project": self.project,
-			"item_code": variant_of or "so_item.item_code",
 			"item": self.item_code,
 			"company": self.company,
 			"sales_order_status": self.sales_order_status