From a9151bd89a6ed7c1c7558e8f62b744d3fd843154 Mon Sep 17 00:00:00 2001
From: ximinliang <ximinliang@tencent.com>
Date: Sat, 17 May 2025 15:35:21 +0800
Subject: [PATCH] add get_date and get_time for null_if func

---
 mysql-test/r/func_if.result | 18 ++++++++++++++++++
 mysql-test/t/func_if.test   | 11 +++++++++++
 sql/item_cmpfunc.cc         | 17 +++++++++++++++++
 sql/item_cmpfunc.h          |  2 ++
 4 files changed, 48 insertions(+)

diff --git a/mysql-test/r/func_if.result b/mysql-test/r/func_if.result
index 3594fee3ceee..7ce6cefb5ae9 100644
--- a/mysql-test/r/func_if.result
+++ b/mysql-test/r/func_if.result
@@ -367,3 +367,21 @@ COALESCE(CASE WHEN x THEN NULL ELSE NULL END, x)
 SELECT COALESCE(COALESCE(NULL, NULL), x) FROM t EXCEPT SELECT 1;
 COALESCE(COALESCE(NULL, NULL), x)
 DROP TABLE t;
+#
+# Bug #0000: WRONG RESULT WHEN CAST RESULT OF NULLIF AS DATE OR TIME
+#
+SELECT CAST(NULLIF('1996-11-21 19:40:27', '') AS DATE);
+CAST(NULLIF('1996-11-21 19:40:27', '') AS DATE)
+1996-11-21
+SELECT CAST(NULLIF('1996-11-21 19:40:27', '') AS DATETIME);
+CAST(NULLIF('1996-11-21 19:40:27', '') AS DATETIME)
+1996-11-21 19:40:27
+SELECT CAST(NULLIF('19:40:27', '') AS TIME);
+CAST(NULLIF('19:40:27', '') AS TIME)
+19:40:27
+SELECT CAST(NULLIF('1996-11-21', '1996-11-21') AS DATE);
+CAST(NULLIF('1996-11-21', '1996-11-21') AS DATE)
+NULL
+SELECT CAST(NULLIF(19961121, 0) AS DATE);
+CAST(NULLIF(19961121, 0) AS DATE)
+1996-11-21
diff --git a/mysql-test/t/func_if.test b/mysql-test/t/func_if.test
index a53c6a1eb855..943b8cd079f1 100644
--- a/mysql-test/t/func_if.test
+++ b/mysql-test/t/func_if.test
@@ -322,3 +322,14 @@ SELECT COALESCE(IF(x, NULL, NULL), x) FROM t EXCEPT SELECT 1;
 SELECT COALESCE(CASE WHEN x THEN NULL ELSE NULL END, x) FROM t EXCEPT SELECT 1;
 SELECT COALESCE(COALESCE(NULL, NULL), x) FROM t EXCEPT SELECT 1;
 DROP TABLE t;
+
+
+--echo #
+--echo # Bug #0000: WRONG RESULT WHEN CAST RESULT OF NULLIF AS DATE OR TIME
+--echo #
+
+SELECT CAST(NULLIF('1996-11-21 19:40:27', '') AS DATE);
+SELECT CAST(NULLIF('1996-11-21 19:40:27', '') AS DATETIME);
+SELECT CAST(NULLIF('19:40:27', '') AS TIME);
+SELECT CAST(NULLIF('1996-11-21', '1996-11-21') AS DATE);
+SELECT CAST(NULLIF(19961121, 0) AS DATE);
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 51481aa72a1b..b67091163a6d 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -3917,6 +3917,23 @@ bool Item_func_nullif::val_json(Json_wrapper *wr) {
   return res;
 }
 
+bool Item_func_nullif::get_date(MYSQL_TIME *res, my_time_flags_t fuzzy_date) {
+  assert(fixed);
+  if (!cmp.compare()) {
+    null_value = true;
+    return true;
+  }
+  return get_arg0_date(res, fuzzy_date);
+}
+bool Item_func_nullif::get_time(MYSQL_TIME *res) {
+  assert(fixed);
+  if (!cmp.compare()) {
+    null_value = true;
+    return true;
+  }
+  return get_arg0_time(res);
+}
+
 bool Item_func_nullif::is_null() {
   const int result = cmp.compare();
   if (current_thd->is_error()) {
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index b8669532eae0..21235ac9c770 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1607,6 +1607,8 @@ class Item_func_nullif final : public Item_bool_func2 {
   String *val_str(String *str) override;
   my_decimal *val_decimal(my_decimal *) override;
   bool val_json(Json_wrapper *wr) override;
+  bool get_date(MYSQL_TIME *res, my_time_flags_t fuzzy_date) override;
+  bool get_time(MYSQL_TIME *ltime) override;
   Item_result result_type() const override { return cached_result_type; }
   enum_field_types default_data_type() const override {
     return MYSQL_TYPE_VARCHAR;