From e474f7547bcf6ba1cabd322ca90f3d97be73ee62 Mon Sep 17 00:00:00 2001
From: Xingyu Yang <xingyuyang@tencent.com>
Date: Mon, 9 Feb 2026 17:01:13 +0800
Subject: [PATCH] [bugfix] Inconsistent query results when using <=> to compare
 row data with empty set subquery result

---
 sql/item_subselect.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index e4466735d8c..c39c0bbdbaf 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -3072,6 +3072,13 @@ bool SubqueryWithResult::exec(THD *thd) {
   char const *save_where = thd->where;
   const bool res = unit->execute(thd);
   thd->where = save_where;
+  if (item->substype() == Item_subselect::SINGLEROW_SUBS && item->null_value) {
+    Item_singlerow_subselect *item_singlerow =
+        down_cast<Item_singlerow_subselect *>(this->item);
+    for (uint i = 0; i < item_singlerow->cols(); ++i) {
+      down_cast<Item_cache *>(item_singlerow->element_index(i))->store_null();
+    }
+  }
   return res;
 }
 
-- 
2.43.5