diff --git a/erpnext/stock/doctype/delivery_note/delivery_note.py b/erpnext/stock/doctype/delivery_note/delivery_note.py
index 7bfd275ee2a..7f524c82912 100644
--- a/erpnext/stock/doctype/delivery_note/delivery_note.py
+++ b/erpnext/stock/doctype/delivery_note/delivery_note.py
@@ -261,12 +261,10 @@ class DeliveryNote(SellingController):
 	def set_actual_qty(self):
 		for d in self.get("items"):
 			if d.item_code and d.warehouse:
-				actual_qty = frappe.db.sql(
-					"""select actual_qty from `tabBin`
-					where item_code = %s and warehouse = %s""",
-					(d.item_code, d.warehouse),
+				actual_qty = frappe.db.get_value(
+					"Bin", {"item_code": d.item_code, "warehouse": d.warehouse}, "actual_qty"
 				)
-				d.actual_qty = actual_qty and flt(actual_qty[0][0]) or 0
+				d.actual_qty = flt(actual_qty) or 0
 
 	def so_required(self):
 		"""check in manage account if sales order required or not"""
@@ -385,11 +383,10 @@ class DeliveryNote(SellingController):
 	def validate_proj_cust(self):
 		"""check for does customer belong to same project as entered.."""
 		if self.project and self.customer:
-			res = frappe.db.sql(
-				"""select name from `tabProject`
-				where name = %s and (customer = %s or
-					ifnull(customer,'')='')""",
-				(self.project, self.customer),
+			res = frappe.get_all(
+				"Project",
+				filters={"name": self.project},
+				or_filters=[["customer", "=", self.customer], ["customer", "is", "not set"]],
 			)
 			if not res:
 				frappe.throw(
@@ -604,20 +601,20 @@ class DeliveryNote(SellingController):
 		PackingService(self).validate_packed_qty()
 
 	def check_next_docstatus(self):
-		submit_rv = frappe.db.sql(
-			"""select t1.name
-			from `tabSales Invoice` t1,`tabSales Invoice Item` t2
-			where t1.name = t2.parent and t2.delivery_note = %s and t1.docstatus = 1""",
-			(self.name),
+		submit_rv = frappe.get_all(
+			"Sales Invoice Item",
+			filters={"delivery_note": self.name, "docstatus": 1},
+			fields=["parent"],
+			as_list=True,
 		)
 		if submit_rv:
 			frappe.throw(_("Sales Invoice {0} has already been submitted").format(submit_rv[0][0]))
 
-		submit_in = frappe.db.sql(
-			"""select t1.name
-			from `tabInstallation Note` t1, `tabInstallation Note Item` t2
-			where t1.name = t2.parent and t2.prevdoc_docname = %s and t1.docstatus = 1""",
-			(self.name),
+		submit_in = frappe.get_all(
+			"Installation Note Item",
+			filters={"prevdoc_docname": self.name, "docstatus": 1},
+			fields=["parent"],
+			as_list=True,
 		)
 		if submit_in:
 			frappe.throw(_("Installation Note {0} has already been submitted").format(submit_in[0][0]))
diff --git a/erpnext/stock/doctype/delivery_note/test_delivery_note.py b/erpnext/stock/doctype/delivery_note/test_delivery_note.py
index aca8491946d..68cb91a979c 100644
--- a/erpnext/stock/doctype/delivery_note/test_delivery_note.py
+++ b/erpnext/stock/doctype/delivery_note/test_delivery_note.py
@@ -3376,6 +3376,68 @@ class TestDeliveryNote(ERPNextTestSuite):
 		dn.items[0].stock_qty = 2
 		dn.save()
 
+	def test_validate_proj_cust_matches_project_customer(self):
+		"""validate_proj_cust must reject a DN whose customer differs from the project's customer,
+		and accept one when the project has no customer (the ifnull(customer,'')='' / `is not set`
+		branch of the converted or_filters)."""
+		mismatch_project = frappe.get_doc(
+			{
+				"doctype": "Project",
+				"project_name": "_Test DN Project Mismatch",
+				"company": "_Test Company",
+				"customer": "_Test Customer 1",
+			}
+		).insert()
+		dn = create_delivery_note(customer="_Test Customer", do_not_save=True)
+		dn.project = mismatch_project.name
+		with self.assertRaises(frappe.ValidationError) as cm:
+			dn.insert()
+		self.assertIn("does not belong to project", str(cm.exception))
+
+		# A project with no customer must pass via the empty-string/NULL or_filters branch.
+		open_project = frappe.get_doc(
+			{
+				"doctype": "Project",
+				"project_name": "_Test DN Project No Customer",
+				"company": "_Test Company",
+			}
+		).insert()
+		self.assertFalse(open_project.customer)
+		dn2 = create_delivery_note(customer="_Test Customer", do_not_save=True)
+		dn2.project = open_project.name
+		dn2.insert()  # must not raise
+		self.assertTrue(dn2.name)
+
+	def test_check_next_docstatus_blocks_cancel_with_submitted_invoice(self):
+		"""check_next_docstatus must block cancelling a DN once a submitted Sales Invoice draws from
+		it — covers the converted child-table get_all (Sales Invoice Item, docstatus=1)."""
+		dn = create_delivery_note()  # submitted, simple _Test Item
+		si = make_sales_invoice(dn.name)
+		si.insert()
+		si.submit()
+
+		dn.load_from_db()
+		with self.assertRaises(frappe.ValidationError) as cm:
+			dn.cancel()
+		self.assertIn("has already been submitted", str(cm.exception))
+
+	def test_cancel_packing_slips_cancels_submitted_slips(self):
+		"""cancel_packing_slips must cancel the DN's submitted Packing Slips — covers the converted
+		get_all(pluck=name) lookup and the pluck-aware iteration."""
+		from erpnext.stock.doctype.delivery_note.mapper import make_packing_slip
+		from erpnext.stock.doctype.delivery_note.services.packing import PackingService
+
+		dn = create_delivery_note(do_not_submit=True)  # draft, so a Packing Slip can be mapped
+		ps = make_packing_slip(dn.name)
+		ps.save()
+		ps.submit()
+		dn.submit()
+		self.assertEqual(frappe.db.get_value("Packing Slip", ps.name, "docstatus"), 1)
+
+		PackingService(dn).cancel_packing_slips()
+
+		self.assertEqual(frappe.db.get_value("Packing Slip", ps.name, "docstatus"), 2)
+
 
 def create_delivery_note(**args):
 	dn = frappe.new_doc("Delivery Note")