diff --git a/erpnext/stock/doctype/material_request/material_request.py b/erpnext/stock/doctype/material_request/material_request.py
index c020ab35f90..a806b5b6a31 100644
--- a/erpnext/stock/doctype/material_request/material_request.py
+++ b/erpnext/stock/doctype/material_request/material_request.py
@@ -13,7 +13,7 @@ from frappe import _, msgprint
 from frappe.model.document import Document
 from frappe.query_builder import Order
 from frappe.query_builder.functions import Sum
-from frappe.utils import cint, cstr, flt, get_link_to_form, getdate, new_line_sep, nowdate
+from frappe.utils import cint, flt, get_datetime, get_link_to_form, getdate, new_line_sep, nowdate
 
 from erpnext.buying.utils import check_on_hold_or_closed_status, validate_for_items
 from erpnext.controllers.buying_controller import BuyingController
@@ -125,21 +125,24 @@ class MaterialRequest(BuyingController):
 
 		for so_no in so_items.keys():
 			for item in so_items[so_no].keys():
-				already_indented = frappe.db.sql(
-					"""select sum(qty)
-					from `tabMaterial Request Item`
-					where item_code = %s and sales_order = %s and
-					docstatus = 1 and parent != %s""",
-					(item, so_no, self.name),
+				already_indented = frappe.get_all(
+					"Material Request Item",
+					filters={
+						"item_code": item,
+						"sales_order": so_no,
+						"docstatus": 1,
+						"parent": ["!=", self.name],
+					},
+					fields=[{"SUM": "qty", "as": "qty"}],
 				)
-				already_indented = already_indented and flt(already_indented[0][0]) or 0
+				already_indented = flt(already_indented[0].qty) if already_indented else 0
 
-				actual_so_qty = frappe.db.sql(
-					"""select sum(stock_qty) from `tabSales Order Item`
-					where parent = %s and item_code = %s and docstatus = 1""",
-					(so_no, item),
+				actual_so_qty = frappe.get_all(
+					"Sales Order Item",
+					filters={"parent": so_no, "item_code": item, "docstatus": 1},
+					fields=[{"SUM": "stock_qty", "as": "stock_qty"}],
 				)
-				actual_so_qty = actual_so_qty and flt(actual_so_qty[0][0]) or 0
+				actual_so_qty = flt(actual_so_qty[0].stock_qty) if actual_so_qty else 0
 
 				if actual_so_qty and (flt(so_items[so_no][item]) + already_indented > actual_so_qty):
 					frappe.throw(
@@ -249,10 +252,9 @@ class MaterialRequest(BuyingController):
 		self.set_status(update=True, status="Cancelled")
 
 	def check_modified_date(self):
-		mod_db = frappe.db.sql("""select modified from `tabMaterial Request` where name = %s""", self.name)
-		date_diff = frappe.db.sql("""select TIMEDIFF(%s, %s)""", (mod_db[0][0], cstr(self.modified)))
+		mod_db = frappe.db.get_value("Material Request", self.name, "modified")
 
-		if date_diff and date_diff[0][0]:
+		if mod_db and get_datetime(mod_db) != get_datetime(self.modified):
 			frappe.throw(_("{0} {1} has been modified. Please refresh.").format(_(self.doctype), self.name))
 
 	def update_status(self, status):
diff --git a/erpnext/stock/doctype/material_request/test_material_request.py b/erpnext/stock/doctype/material_request/test_material_request.py
index 5406d722b3f..0e1c42c0828 100644
--- a/erpnext/stock/doctype/material_request/test_material_request.py
+++ b/erpnext/stock/doctype/material_request/test_material_request.py
@@ -1191,6 +1191,67 @@ class TestMaterialRequest(ERPNextTestSuite):
 		self.assertEqual(material_request.status, "Transferred")
 		self.assertEqual(material_request.transfer_status, "Completed")
 
+	def test_check_modified_date_detects_concurrent_modification(self):
+		"""check_modified_date must raise when the in-memory doc is stale vs the DB modified
+		timestamp. Covers the converted get_value + get_datetime comparison that replaced the
+		raw MariaDB-only TIMEDIFF (which errors on Postgres); update_status() runs this guard."""
+		from frappe.utils import add_to_date, get_datetime
+
+		mr = make_material_request(qty=10)
+
+		fresh = frappe.get_doc("Material Request", mr.name)
+		# modified matches the DB row -> guard passes.
+		fresh.check_modified_date()
+
+		# Stale in-memory modified -> concurrent-modification guard must fire.
+		fresh.modified = add_to_date(get_datetime(fresh.modified), seconds=-120)
+		with self.assertRaises(frappe.ValidationError) as cm:
+			fresh.check_modified_date()
+		self.assertIn("has been modified", str(cm.exception))
+
+	def test_validate_qty_against_so_blocks_over_request(self):
+		"""validate_qty_against_so must block requesting more than the Sales Order qty, net of
+		already-indented submitted MRs. Covers the converted Sales Order Item and Material Request
+		Item SUM queries. (The guard is currently not wired into validate(), so call it directly.)"""
+		from erpnext.selling.doctype.sales_order.test_sales_order import make_sales_order
+
+		item_code = "_Test Item"
+		so = make_sales_order(item_code=item_code, qty=10)  # submitted -> SO Item stock_qty 10
+
+		def _mr_against_so(qty):
+			mr = frappe.new_doc("Material Request")
+			mr.material_request_type = "Purchase"
+			mr.company = "_Test Company"
+			mr.append(
+				"items",
+				{
+					"item_code": item_code,
+					"qty": qty,
+					"uom": "_Test UOM",
+					"conversion_factor": 1,
+					"schedule_date": today(),
+					"warehouse": "_Test Warehouse - _TC",
+					"sales_order": so.name,
+				},
+			)
+			return mr
+
+		# An already-submitted MR consuming 6 of the SO's 10.
+		mr1 = _mr_against_so(6)
+		mr1.insert()
+		mr1.submit()
+
+		# A new request for 5 more -> already_indented 6 + 5 = 11 > 10 -> must throw.
+		over = _mr_against_so(5)
+		over.insert()
+		with self.assertRaises(frappe.ValidationError) as cm:
+			over.validate_qty_against_so()
+		self.assertIn("maximum", str(cm.exception))
+
+		# Exactly within the remaining 4 -> 6 + 4 = 10, not greater -> no throw.
+		over.items[0].qty = 4
+		over.validate_qty_against_so()
+
 
 def get_in_transit_warehouse(company):
 	if not frappe.db.exists("Warehouse Type", "Transit"):