diff --git a/be/src/agent/be_exec_version_manager.h b/be/src/agent/be_exec_version_manager.h
index 1cabc38eba..f5213c5408 100644
--- a/be/src/agent/be_exec_version_manager.h
+++ b/be/src/agent/be_exec_version_manager.h
@@ -64,7 +64,7 @@ private:
  *    c. cleared old version of Version 2.
  *    d. unix_timestamp function support timestamp with float for datetimev2, and change nullable mode.
  *    e. change shuffle serialize/deserialize way 
- *    f. the right function outputs NULL when the function contains NULL, substr function returns empty if start > str.length, and change some function nullable mode.
+ *    f. shrink some function's nullable mode.
 */
 constexpr inline int BeExecVersionManager::max_be_exec_version = 3;
 constexpr inline int BeExecVersionManager::min_be_exec_version = 0;
diff --git a/be/src/util/url_coding.cpp b/be/src/util/url_coding.cpp
index 0a5c4144c5..f091e63812 100644
--- a/be/src/util/url_coding.cpp
+++ b/be/src/util/url_coding.cpp
@@ -91,7 +91,7 @@ static void encode_base64_internal(const std::string& in, std::string* out,
     size_t len = in.size();
     // Every 3 source bytes will be encoded into 4 bytes.
     std::unique_ptr<unsigned char[]> buf(new unsigned char[(((len + 2) / 3) * 4)]);
-    const unsigned char* s = reinterpret_cast<const unsigned char*>(in.data());
+    const auto* s = reinterpret_cast<const unsigned char*>(in.data());
     unsigned char* d = buf.get();
     while (len > 2) {
         *d++ = basis[(s[0] >> 2) & 0x3f];
@@ -157,7 +157,7 @@ static short decoding_table[256] = {
 static int mod_table[] = {0, 2, 1};
 
 size_t base64_encode(const unsigned char* data, size_t length, unsigned char* encoded_data) {
-    size_t output_length = (size_t)(4.0 * ceil((double)length / 3.0));
+    auto output_length = (size_t)(4.0 * ceil((double)length / 3.0));
 
     if (encoded_data == nullptr) {
         return 0;
@@ -267,7 +267,7 @@ bool base64_decode(const std::string& in, std::string* out) {
 }
 
 void escape_for_html(const std::string& in, std::stringstream* out) {
-    for (auto& c : in) {
+    for (const auto& c : in) {
         switch (c) {
         case '<':
             (*out) << "&lt;";
diff --git a/be/src/vec/functions/function_string.cpp b/be/src/vec/functions/function_string.cpp
index cce325e89e..ab4ac6c86a 100644
--- a/be/src/vec/functions/function_string.cpp
+++ b/be/src/vec/functions/function_string.cpp
@@ -140,8 +140,8 @@ struct FindInSetOp {
     using ResultDataType = DataTypeInt32;
     using ResultPaddedPODArray = PaddedPODArray<Int32>;
     static void execute(const std::string_view& strl, const std::string_view& strr, int32_t& res) {
-        for (int i = 0; i < strl.length(); ++i) {
-            if (strl[i] == ',') {
+        for (const auto& c : strl) {
+            if (c == ',') {
                 res = 0;
                 return;
             }
@@ -635,18 +635,12 @@ struct UnHexImpl {
     }
 
     static Status vector(const ColumnString::Chars& data, const ColumnString::Offsets& offsets,
-                         ColumnString::Chars& dst_data, ColumnString::Offsets& dst_offsets,
-                         NullMap& null_map) {
+                         ColumnString::Chars& dst_data, ColumnString::Offsets& dst_offsets) {
         auto rows_count = offsets.size();
         dst_offsets.resize(rows_count);
 
         for (int i = 0; i < rows_count; ++i) {
-            if (null_map[i]) {
-                StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
-                continue;
-            }
-
-            auto source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
+            const auto* source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
             size_t srclen = offsets[i] - offsets[i - 1];
 
             if (srclen == 0) {
@@ -666,17 +660,103 @@ struct UnHexImpl {
 
             int outlen = hex_decode(source, srclen, dst);
 
-            if (outlen < 0) {
-                StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
-            } else {
-                StringOP::push_value_string(std::string_view(dst, outlen), i, dst_data,
-                                            dst_offsets);
-            }
+            StringOP::push_value_string(std::string_view(dst, outlen), i, dst_data, dst_offsets);
         }
 
         return Status::OK();
     }
 };
+
+struct UnHexOldImpl {
+    static constexpr auto name = "unhex";
+    using ReturnType = DataTypeString;
+    using ColumnType = ColumnString;
+
+    static bool check_and_decode_one(char& c, const char src_c, bool flag) {
+        int k = flag ? 16 : 1;
+        int value = src_c - '0';
+        // 9 = ('9'-'0')
+        if (value >= 0 && value <= 9) {
+            c += value * k;
+            return true;
+        }
+
+        value = src_c - 'A';
+        // 5 = ('F'-'A')
+        if (value >= 0 && value <= 5) {
+            c += (value + 10) * k;
+            return true;
+        }
+
+        value = src_c - 'a';
+        // 5 = ('f'-'a')
+        if (value >= 0 && value <= 5) {
+            c += (value + 10) * k;
+            return true;
+        }
+        // not in ( ['0','9'], ['a','f'], ['A','F'] )
+        return false;
+    }
+
+    static int hex_decode(const char* src_str, size_t src_len, char* dst_str) {
+        // if str length is odd or 0, return empty string like mysql dose.
+        if ((src_len & 1) != 0 or src_len == 0) {
+            return 0;
+        }
+        //check and decode one character at the same time
+        // character in ( ['0','9'], ['a','f'], ['A','F'] ), return 'NULL' like mysql dose.
+        for (auto i = 0, dst_index = 0; i < src_len; i += 2, dst_index++) {
+            char c = 0;
+            // combine two character into dst_str one character
+            bool left_4bits_flag = check_and_decode_one(c, *(src_str + i), true);
+            bool right_4bits_flag = check_and_decode_one(c, *(src_str + i + 1), false);
+
+            if (!left_4bits_flag || !right_4bits_flag) {
+                return 0;
+            }
+            *(dst_str + dst_index) = c;
+        }
+        return src_len / 2;
+    }
+
+    static Status vector(const ColumnString::Chars& data, const ColumnString::Offsets& offsets,
+                         ColumnString::Chars& dst_data, ColumnString::Offsets& dst_offsets,
+                         NullMap& null_map) {
+        auto rows_count = offsets.size();
+        dst_offsets.resize(rows_count);
+
+        for (int i = 0; i < rows_count; ++i) {
+            if (null_map[i]) {
+                StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
+                continue;
+            }
+            const auto* source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
+            size_t srclen = offsets[i] - offsets[i - 1];
+
+            if (srclen == 0) {
+                StringOP::push_empty_string(i, dst_data, dst_offsets);
+                continue;
+            }
+
+            char dst_array[MAX_STACK_CIPHER_LEN];
+            char* dst = dst_array;
+
+            int cipher_len = srclen / 2;
+            std::unique_ptr<char[]> dst_uptr;
+            if (cipher_len > MAX_STACK_CIPHER_LEN) {
+                dst_uptr.reset(new char[cipher_len]);
+                dst = dst_uptr.get();
+            }
+
+            int outlen = hex_decode(source, srclen, dst);
+
+            StringOP::push_value_string(std::string_view(dst, outlen), i, dst_data, dst_offsets);
+        }
+
+        return Status::OK();
+    }
+};
+
 struct NameStringSpace {
     static constexpr auto name = "space";
 };
@@ -714,22 +794,16 @@ struct ToBase64Impl {
     using ColumnType = ColumnString;
 
     static Status vector(const ColumnString::Chars& data, const ColumnString::Offsets& offsets,
-                         ColumnString::Chars& dst_data, ColumnString::Offsets& dst_offsets,
-                         NullMap& null_map) {
+                         ColumnString::Chars& dst_data, ColumnString::Offsets& dst_offsets) {
         auto rows_count = offsets.size();
         dst_offsets.resize(rows_count);
 
         for (int i = 0; i < rows_count; ++i) {
-            if (null_map[i]) {
-                StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
-                continue;
-            }
-
-            auto source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
+            const auto* source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
             size_t srclen = offsets[i] - offsets[i - 1];
 
             if (srclen == 0) {
-                StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
+                StringOP::push_empty_string(i, dst_data, dst_offsets);
                 continue;
             }
 
@@ -745,12 +819,50 @@ struct ToBase64Impl {
 
             int outlen = base64_encode((const unsigned char*)source, srclen, (unsigned char*)dst);
 
-            if (outlen < 0) {
+            StringOP::push_value_string(std::string_view(dst, outlen), i, dst_data, dst_offsets);
+        }
+        return Status::OK();
+    }
+};
+
+struct ToBase64OldImpl {
+    static constexpr auto name = "to_base64";
+    using ReturnType = DataTypeString;
+    using ColumnType = ColumnString;
+
+    static Status vector(const ColumnString::Chars& data, const ColumnString::Offsets& offsets,
+                         ColumnString::Chars& dst_data, ColumnString::Offsets& dst_offsets,
+                         NullMap& null_map) {
+        auto rows_count = offsets.size();
+        dst_offsets.resize(rows_count);
+
+        for (int i = 0; i < rows_count; ++i) {
+            if (null_map[i]) {
                 StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
-            } else {
-                StringOP::push_value_string(std::string_view(dst, outlen), i, dst_data,
-                                            dst_offsets);
+                continue;
             }
+
+            const auto* source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
+            size_t srclen = offsets[i] - offsets[i - 1];
+
+            if (srclen == 0) {
+                StringOP::push_empty_string(i, dst_data, dst_offsets);
+                continue;
+            }
+
+            char dst_array[MAX_STACK_CIPHER_LEN];
+            char* dst = dst_array;
+
+            int cipher_len = (int)(4.0 * ceil((double)srclen / 3.0));
+            std::unique_ptr<char[]> dst_uptr;
+            if (cipher_len > MAX_STACK_CIPHER_LEN) {
+                dst_uptr.reset(new char[cipher_len]);
+                dst = dst_uptr.get();
+            }
+
+            int outlen = base64_encode((const unsigned char*)source, srclen, (unsigned char*)dst);
+
+            StringOP::push_value_string(std::string_view(dst, outlen), i, dst_data, dst_offsets);
         }
         return Status::OK();
     }
@@ -773,11 +885,11 @@ struct FromBase64Impl {
                 continue;
             }
 
-            auto source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
+            const auto* source = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
             size_t srclen = offsets[i] - offsets[i - 1];
 
             if (srclen == 0) {
-                StringOP::push_null_string(i, dst_data, dst_offsets, null_map);
+                StringOP::push_empty_string(i, dst_data, dst_offsets);
                 continue;
             }
 
@@ -946,8 +1058,11 @@ using FunctionToUpper = FunctionStringToString<TransferImpl<NameToUpper>, NameTo
 
 using FunctionToInitcap = FunctionStringToString<InitcapImpl, NameToInitcap>;
 
-using FunctionUnHex = FunctionStringOperateToNullType<UnHexImpl>;
-using FunctionToBase64 = FunctionStringOperateToNullType<ToBase64Impl>;
+using FunctionUnHex = FunctionStringEncode<UnHexImpl>;
+using FunctionToBase64 = FunctionStringEncode<ToBase64Impl>;
+
+using FunctionUnHexOld = FunctionStringOperateToNullType<UnHexOldImpl>;
+using FunctionToBase64Old = FunctionStringOperateToNullType<ToBase64OldImpl>;
 using FunctionFromBase64 = FunctionStringOperateToNullType<FromBase64Impl>;
 
 using FunctionStringAppendTrailingCharIfAbsent =
@@ -1023,6 +1138,8 @@ void register_function_string(SimpleFunctionFactory& factory) {
     factory.register_alternative_function<FunctionRightOld>();
     factory.register_alternative_function<FunctionSubstringIndexOld>();
     factory.register_alternative_function<FunctionStringRepeatOld>();
+    factory.register_alternative_function<FunctionUnHexOld>();
+    factory.register_alternative_function<FunctionToBase64Old>();
 
     factory.register_alias(FunctionLeft::name, "strleft");
     factory.register_alias(FunctionRight::name, "strright");
diff --git a/be/src/vec/functions/function_totype.h b/be/src/vec/functions/function_totype.h
index 39c8cba09e..e6722a6941 100644
--- a/be/src/vec/functions/function_totype.h
+++ b/be/src/vec/functions/function_totype.h
@@ -474,7 +474,7 @@ public:
         auto& col_ptr = block.get_by_position(arguments[0]).column;
 
         auto res = Impl::ColumnType::create();
-        if (const ColumnString* col = check_and_get_column<ColumnString>(col_ptr.get())) {
+        if (const auto* col = check_and_get_column<ColumnString>(col_ptr.get())) {
             auto col_res = Impl::ColumnType::create();
             static_cast<void>(Impl::vector(col->get_chars(), col->get_offsets(),
                                            col_res->get_chars(), col_res->get_offsets(),
@@ -490,4 +490,38 @@ public:
     }
 };
 
+template <typename Impl>
+class FunctionStringEncode : public IFunction {
+public:
+    static constexpr auto name = Impl::name;
+
+    static FunctionPtr create() { return std::make_shared<FunctionStringEncode>(); }
+
+    String get_name() const override { return name; }
+
+    size_t get_number_of_arguments() const override { return 1; }
+
+    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {
+        return std::make_shared<typename Impl::ReturnType>();
+    }
+
+    Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,
+                        size_t result, size_t input_rows_count) const override {
+        auto& col_ptr = block.get_by_position(arguments[0]).column;
+
+        auto res = Impl::ColumnType::create();
+        if (const auto* col = check_and_get_column<ColumnString>(col_ptr.get())) {
+            auto col_res = Impl::ColumnType::create();
+            static_cast<void>(Impl::vector(col->get_chars(), col->get_offsets(),
+                                           col_res->get_chars(), col_res->get_offsets()));
+            block.replace_by_position(result, std::move(col_res));
+        } else {
+            return Status::RuntimeError("Illegal column {} of argument of function {}",
+                                        block.get_by_position(arguments[0]).column->get_name(),
+                                        get_name());
+        }
+        return Status::OK();
+    }
+};
+
 } // namespace doris::vectorized
diff --git a/be/test/vec/function/function_string_test.cpp b/be/test/vec/function/function_string_test.cpp
index 5425b0cd08..39a9dca901 100644
--- a/be/test/vec/function/function_string_test.cpp
+++ b/be/test/vec/function/function_string_test.cpp
@@ -482,7 +482,7 @@ TEST(function_string_test, function_to_base64_test) {
     DataSet data_set = {{{std::string("asd你好")}, {std::string("YXNk5L2g5aW9")}},
                         {{std::string("hello world")}, {std::string("aGVsbG8gd29ybGQ=")}},
                         {{std::string("HELLO,!^%")}, {std::string("SEVMTE8sIV4l")}},
-                        {{std::string("")}, {Null()}},
+                        {{std::string("")}, {std::string("")}},
                         {{std::string("MYtestSTR")}, {std::string("TVl0ZXN0U1RS")}},
                         {{std::string("ò&ø")}, {std::string("w7Imw7g=")}}};
 
@@ -496,7 +496,7 @@ TEST(function_string_test, function_from_base64_test) {
     DataSet data_set = {{{std::string("YXNk5L2g5aW9")}, {std::string("asd你好")}},
                         {{std::string("aGVsbG8gd29ybGQ=")}, {std::string("hello world")}},
                         {{std::string("SEVMTE8sIV4l")}, {std::string("HELLO,!^%")}},
-                        {{std::string("")}, {Null()}},
+                        {{std::string("")}, {std::string("")}},
                         {{std::string("TVl0ZXN0U1RS")}, {std::string("MYtestSTR")}},
                         {{std::string("w7Imw7g=")}, {std::string("ò&ø")}},
                         {{std::string("ò&ø")}, {Null()}},
diff --git a/docs/en/docs/sql-manual/sql-functions/string-functions/from-base64.md b/docs/en/docs/sql-manual/sql-functions/string-functions/from-base64.md
index bb2d285a08..ea6cfe3745 100644
--- a/docs/en/docs/sql-manual/sql-functions/string-functions/from-base64.md
+++ b/docs/en/docs/sql-manual/sql-functions/string-functions/from-base64.md
@@ -31,7 +31,7 @@ under the License.
 `VARCHAR from_base64(VARCHAR str)`
 
 
-Returns the result of Base64 decoding the input string
+Returns the result of Base64 decoding the input string, NULL is returned when the input string is incorrect (with non-Base64 encoded characters).
 
 ### example
 
diff --git a/docs/zh-CN/docs/sql-manual/sql-functions/string-functions/from-base64.md b/docs/zh-CN/docs/sql-manual/sql-functions/string-functions/from-base64.md
index 34a6c488e5..f708e8a2fb 100644
--- a/docs/zh-CN/docs/sql-manual/sql-functions/string-functions/from-base64.md
+++ b/docs/zh-CN/docs/sql-manual/sql-functions/string-functions/from-base64.md
@@ -31,7 +31,7 @@ under the License.
 `VARCHAR from_base64(VARCHAR str)`
 
 
-返回对输入的字符串进行Base64解码后的结果
+返回对输入的字符串进行Base64解码后的结果，当输入字符串不正确时（出现非Base64编码后可能出现的字符）将会返回NULL
 
 ### example
 
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/ToBase64.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/ToBase64.java
index 99a1722dae..dab8e46ec3 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/ToBase64.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/ToBase64.java
@@ -19,8 +19,8 @@ package org.apache.doris.nereids.trees.expressions.functions.scalar;
 
 import org.apache.doris.catalog.FunctionSignature;
 import org.apache.doris.nereids.trees.expressions.Expression;
-import org.apache.doris.nereids.trees.expressions.functions.AlwaysNullable;
 import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
+import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
 import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
 import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
 import org.apache.doris.nereids.types.StringType;
@@ -34,7 +34,7 @@ import java.util.List;
  * ScalarFunction 'to_base64'. This class is generated by GenerateFunction.
  */
 public class ToBase64 extends ScalarFunction
-        implements UnaryExpression, ExplicitlyCastableSignature, AlwaysNullable {
+        implements UnaryExpression, ExplicitlyCastableSignature, PropagateNullable {
 
     public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
             FunctionSignature.ret(StringType.INSTANCE).args(StringType.INSTANCE)
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/Unhex.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/Unhex.java
index d500eef41e..4fb1cc37be 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/Unhex.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/Unhex.java
@@ -19,8 +19,8 @@ package org.apache.doris.nereids.trees.expressions.functions.scalar;
 
 import org.apache.doris.catalog.FunctionSignature;
 import org.apache.doris.nereids.trees.expressions.Expression;
-import org.apache.doris.nereids.trees.expressions.functions.AlwaysNullable;
 import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
+import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
 import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
 import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
 import org.apache.doris.nereids.types.StringType;
@@ -35,7 +35,7 @@ import java.util.List;
  * ScalarFunction 'unhex'. This class is generated by GenerateFunction.
  */
 public class Unhex extends ScalarFunction
-        implements UnaryExpression, ExplicitlyCastableSignature, AlwaysNullable {
+        implements UnaryExpression, ExplicitlyCastableSignature, PropagateNullable {
 
     public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
             FunctionSignature.ret(VarcharType.SYSTEM_DEFAULT).args(VarcharType.SYSTEM_DEFAULT),
diff --git a/gensrc/script/doris_builtins_functions.py b/gensrc/script/doris_builtins_functions.py
index 3fbe079eb3..1277f72db6 100644
--- a/gensrc/script/doris_builtins_functions.py
+++ b/gensrc/script/doris_builtins_functions.py
@@ -1405,8 +1405,8 @@ visible_functions = {
         [['truncate'], 'DECIMAL64', ['DECIMAL64', 'INT'], ''],
         [['truncate'], 'DECIMAL128', ['DECIMAL128', 'INT'], ''],
         
-        [['unhex'], 'VARCHAR', ['VARCHAR'], 'ALWAYS_NULLABLE'],
-        [['unhex'], 'STRING', ['STRING'], 'ALWAYS_NULLABLE']
+        [['unhex'], 'VARCHAR', ['VARCHAR'], 'DEPEND_ON_ARGUMENT'],
+        [['unhex'], 'STRING', ['STRING'], 'DEPEND_ON_ARGUMENT']
     ],
 
     # Conditional Functions
@@ -1908,8 +1908,8 @@ visible_functions = {
         [['sm4_encrypt'], 'STRING', ['STRING', 'STRING', 'STRING', 'STRING'], 'ALWAYS_NULLABLE'],
         [['sm4_decrypt'], 'STRING', ['STRING', 'STRING', 'STRING', 'STRING'], 'ALWAYS_NULLABLE'],
         [['from_base64'], 'STRING', ['STRING'], 'ALWAYS_NULLABLE'],
-        [['to_base64'], 'STRING', ['STRING'], 'ALWAYS_NULLABLE'],
-        [['to_base64'], 'VARCHAR', ['VARCHAR'], 'ALWAYS_NULLABLE']
+        [['to_base64'], 'STRING', ['STRING'], 'DEPEND_ON_ARGUMENT'],
+        [['to_base64'], 'VARCHAR', ['VARCHAR'], 'DEPEND_ON_ARGUMENT']
     ],
 
     # for compatable with MySQL
diff --git a/regression-test/data/nereids_p0/sql_functions/string_functions/test_string_function.out b/regression-test/data/nereids_p0/sql_functions/string_functions/test_string_function.out
index c0bffd9e92..7f2e30b5c1 100644
--- a/regression-test/data/nereids_p0/sql_functions/string_functions/test_string_function.out
+++ b/regression-test/data/nereids_p0/sql_functions/string_functions/test_string_function.out
@@ -104,6 +104,12 @@ A
 -- !sql --
 AB
 
+-- !sql --
+
+
+-- !sql --
+\N
+
 -- !sql --
 2
 
diff --git a/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out b/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out
index fef380ebc7..e3ca494c63 100644
Binary files a/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out and b/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out differ
diff --git a/regression-test/suites/nereids_p0/sql_functions/string_functions/test_string_function.groovy b/regression-test/suites/nereids_p0/sql_functions/string_functions/test_string_function.groovy
index b1eb8aeefa..64fcc2e372 100644
--- a/regression-test/suites/nereids_p0/sql_functions/string_functions/test_string_function.groovy
+++ b/regression-test/suites/nereids_p0/sql_functions/string_functions/test_string_function.groovy
@@ -73,6 +73,8 @@ suite("test_string_function") {
     qt_sql "select unhex('68656C6C6F2C646F726973');"
     qt_sql "select unhex('41');"
     qt_sql "select unhex('4142');"
+    qt_sql "select unhex('');"
+    qt_sql "select unhex(NULL);"
 
     qt_sql "select instr(\"abc\", \"b\");"
     qt_sql "select instr(\"abc\", \"d\");"
diff --git a/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy b/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy
index f43941870b..2f5b49aa22 100644
--- a/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy
+++ b/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy
@@ -68,6 +68,8 @@ suite("test_string_function", "arrow_flight_sql") {
     qt_sql "select unhex('68656C6C6F2C646F726973');"
     qt_sql "select unhex('41');"
     qt_sql "select unhex('4142');"
+    qt_sql "select unhex('');"
+    qt_sql "select unhex(NULL);"
 
     qt_sql_instr "select instr(\"abc\", \"b\");"
     qt_sql_instr "select instr(\"abc\", \"d\");"