From 6f999aa39921673280eae9057dd592636e0f5622 Mon Sep 17 00:00:00 2001
From: HNOONa-0 <hanyahmed11811@gmail.com>
Date: Mon, 16 Mar 2026 18:58:39 +0200
Subject: [PATCH] MDEV-39043: String '0' sets the ENUM to an empty string

This fixes the string evaluation logic for ENUM types
so the literal string '0' is treated as index 0
---
 mysql-test/main/type_enum.result | 14 ++++++++++++++
 mysql-test/main/type_enum.test   | 15 +++++++++++++++
 sql/field.cc                     |  2 +-
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/type_enum.result b/mysql-test/main/type_enum.result
index 311875d4aa692..8eabab22997b6 100644
--- a/mysql-test/main/type_enum.result
+++ b/mysql-test/main/type_enum.result
@@ -2570,3 +2570,17 @@ Note	1105	Cannot use key parts with `test`.`t1`.`indexed_col` in the rewritten c
 DROP TABLE t2;
 DROP TABLE t1;
 SET note_verbosity=DEFAULT;
+#
+# MDEV-39043 ENUM can be set to empty string by giving an index value as string "0"
+#
+set sql_mode=STRICT_ALL_TABLES;
+create table t1 (a enum('Value1', 'Value2') NOT NULL DEFAULT 'Value1');
+insert into t1 values ('0');
+ERROR 01000: Data truncated for column 'a' at row 1
+select * from t1;
+a
+drop table t1;
+set sql_mode=default;
+#
+# End of 10.6 tests
+#
diff --git a/mysql-test/main/type_enum.test b/mysql-test/main/type_enum.test
index 5276c6ff04c73..01c3f52cc7149 100644
--- a/mysql-test/main/type_enum.test
+++ b/mysql-test/main/type_enum.test
@@ -580,3 +580,18 @@ DELIMITER ;$$
 --source unusable_keys_joins.inc
 DROP TABLE t1;
 SET note_verbosity=DEFAULT;
+
+--echo #
+--echo # MDEV-39043 ENUM can be set to empty string by giving an index value as string "0"
+--echo #
+set sql_mode=STRICT_ALL_TABLES;
+create table t1 (a enum('Value1', 'Value2') NOT NULL DEFAULT 'Value1');
+--error WARN_DATA_TRUNCATED
+insert into t1 values ('0');
+select * from t1;
+drop table t1;
+set sql_mode=default;
+
+--echo #
+--echo # End of 10.6 tests
+--echo #
diff --git a/sql/field.cc b/sql/field.cc
index 6b4c089e830c6..2d43604d4da7f 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -9401,7 +9401,7 @@ int Field_enum::store(const char *from,size_t length,CHARSET_INFO *cs)
       /* This is for reading numbers with LOAD DATA INFILE */
       char *end;
       tmp=(uint) cs->strntoul(from,length,10,&end,&err);
-      if (err || end != from+length || tmp > typelib->count)
+      if (err || end != from+length || !tmp || tmp > typelib->count)
       {
 	tmp=0;
 	set_warning(WARN_DATA_TRUNCATED, 1);