diff --git a/src/max_min_by.rs b/src/max_min_by.rs
index 4c8399d..bfa3754 100644
--- a/src/max_min_by.rs
+++ b/src/max_min_by.rs
@@ -45,7 +45,10 @@ fn get_min_max_by_result_type(
     match &input_types[0] {
         arrow::datatypes::DataType::Dictionary(_, dict_value_type) => {
             // x add checker, if the value type is complex data type
-            Ok(vec![dict_value_type.deref().clone()])
+            let mut result = vec![dict_value_type.deref().clone()];
+            // Preserve all other argument types
+            result.extend_from_slice(&input_types[1..]);
+            Ok(result)
         }
         _ => Ok(input_types.to_vec()),
     }
@@ -207,3 +210,261 @@ impl logical_expr::AggregateUDFImpl for MinByFunction {
         Some(Box::new(simplify))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use datafusion::arrow::array::ArrayAccessor;
+    use datafusion::{arrow, datasource, error, prelude};
+    use std::sync;
+
+    const TEST_TABLE_NAME: &str = "types";
+    const STRING_COLUMN_NAME: &str = "string";
+    const DICTIONARY_COLUMN_NAME: &str = "dict_string";
+    const INT64_COLUMN_NAME: &str = "int64";
+    const FLOAT64_COLUMN_NAME: &str = "float64";
+
+    const MIN_STRING_VALUE: &str = "a";
+    const MID_STRING_VALUE: &str = "b";
+    const MAX_STRING_VALUE: &str = "c";
+    const MIN_FLOAT_VALUE: f64 = 0.25;
+    const MID_FLOAT_VALUE: f64 = 0.5;
+    const MAX_FLOAT_VALUE: f64 = 0.75;
+    const MIN_INT_VALUE: i64 = -1;
+    const MID_INT_VALUE: i64 = 0;
+    const MAX_INT_VALUE: i64 = 1;
+    const MIN_DICTIONARY_VALUE: &str = "a";
+    const MID_DICTIONARY_VALUE: &str = "b";
+    const MAX_DICTIONARY_VALUE: &str = "c";
+
+    fn test_schema() -> sync::Arc<arrow::datatypes::Schema> {
+        sync::Arc::new(arrow::datatypes::Schema::new(vec![
+            arrow::datatypes::Field::new(
+                STRING_COLUMN_NAME,
+                arrow::datatypes::DataType::Utf8,
+                false,
+            ),
+            arrow::datatypes::Field::new_dictionary(
+                DICTIONARY_COLUMN_NAME,
+                arrow::datatypes::DataType::Int32,
+                arrow::datatypes::DataType::Utf8,
+                false,
+            ),
+            arrow::datatypes::Field::new(
+                INT64_COLUMN_NAME,
+                arrow::datatypes::DataType::Int64,
+                false,
+            ),
+            arrow::datatypes::Field::new(
+                FLOAT64_COLUMN_NAME,
+                arrow::datatypes::DataType::Float64,
+                false,
+            ),
+        ]))
+    }
+
+    fn test_data(
+        schema: sync::Arc<arrow::datatypes::Schema>,
+    ) -> Vec<arrow::record_batch::RecordBatch> {
+        vec![
+            arrow::record_batch::RecordBatch::try_new(
+                schema,
+                vec![
+                    sync::Arc::new(arrow::array::StringArray::from(vec![
+                        MID_STRING_VALUE,
+                        MIN_STRING_VALUE,
+                        MAX_STRING_VALUE,
+                    ])),
+                    sync::Arc::new(
+                        vec![
+                            Some(MID_DICTIONARY_VALUE),
+                            Some(MIN_DICTIONARY_VALUE),
+                            Some(MAX_DICTIONARY_VALUE),
+                        ]
+                        .into_iter()
+                        .collect::<arrow::array::DictionaryArray<arrow::datatypes::Int32Type>>(),
+                    ),
+                    sync::Arc::new(arrow::array::Int64Array::from(vec![
+                        MID_INT_VALUE,
+                        MIN_INT_VALUE,
+                        MAX_INT_VALUE,
+                    ])),
+                    sync::Arc::new(arrow::array::Float64Array::from(vec![
+                        MID_FLOAT_VALUE,
+                        MIN_FLOAT_VALUE,
+                        MAX_FLOAT_VALUE,
+                    ])),
+                ],
+            )
+            .unwrap(),
+        ]
+    }
+
+    fn test_ctx() -> datafusion::common::Result<prelude::SessionContext> {
+        let schema = test_schema();
+        let data = test_data(schema.clone());
+        let table = datasource::MemTable::try_new(schema, vec![data])?;
+        let ctx = prelude::SessionContext::new();
+        ctx.register_table(TEST_TABLE_NAME, sync::Arc::new(table))?;
+        Ok(ctx)
+    }
+
+    async fn extract_single_value<T, A>(df: prelude::DataFrame) -> error::Result<T>
+    where
+        A: arrow::array::Array + 'static,
+        for<'a> &'a A: arrow::array::ArrayAccessor,
+        for<'a> <&'a A as arrow::array::ArrayAccessor>::Item: Into<T>,
+    {
+        let results = df.collect().await?;
+        let col = results[0].column(0);
+        let v1 = col.as_any().downcast_ref::<A>().unwrap();
+        let value = v1.value(0).into();
+        Ok(value)
+    }
+
+    #[cfg(test)]
+    mod max_by {
+        use super::*;
+
+        #[tokio::test]
+        async fn test_max_by_string_int() -> error::Result<()> {
+            let query = format!(
+                "SELECT max_by({}, {}) FROM {}",
+                STRING_COLUMN_NAME, INT64_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<String, arrow::array::StringArray>(df).await?;
+            assert_eq!(result, MAX_STRING_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_string_float() -> error::Result<()> {
+            let query = format!(
+                "SELECT max_by({}, {}) FROM {}",
+                STRING_COLUMN_NAME, FLOAT64_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<String, arrow::array::StringArray>(df).await?;
+            assert_eq!(result, MAX_STRING_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_float_string() -> error::Result<()> {
+            let query = format!(
+                "SELECT max_by({}, {}) FROM {}",
+                FLOAT64_COLUMN_NAME, STRING_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<f64, arrow::array::Float64Array>(df).await?;
+            assert_eq!(result, MAX_FLOAT_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_int_string() -> error::Result<()> {
+            let query = format!(
+                "SELECT max_by({}, {}) FROM {}",
+                INT64_COLUMN_NAME, STRING_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<i64, arrow::array::Int64Array>(df).await?;
+            assert_eq!(result, MAX_INT_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_dictionary_int() -> error::Result<()> {
+            let query = format!(
+                "SELECT max_by({}, {}) FROM {}",
+                DICTIONARY_COLUMN_NAME, INT64_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<String, arrow::array::StringArray>(df).await?;
+            assert_eq!(result, MAX_DICTIONARY_VALUE);
+            Ok(())
+        }
+
+        fn ctx() -> error::Result<prelude::SessionContext> {
+            let ctx = test_ctx()?;
+            let max_by_udaf = MaxByFunction::new();
+            ctx.register_udaf(max_by_udaf.into());
+            Ok(ctx)
+        }
+    }
+
+    #[cfg(test)]
+    mod min_by {
+
+        use super::*;
+
+        #[tokio::test]
+        async fn test_min_by_string_int() -> error::Result<()> {
+            let query = format!(
+                "SELECT min_by({}, {}) FROM {}",
+                STRING_COLUMN_NAME, INT64_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<String, arrow::array::StringArray>(df).await?;
+            assert_eq!(result, MIN_STRING_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_string_float() -> error::Result<()> {
+            let query = format!(
+                "SELECT min_by({}, {}) FROM {}",
+                STRING_COLUMN_NAME, FLOAT64_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<String, arrow::array::StringArray>(df).await?;
+            assert_eq!(result, MIN_STRING_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_float_string() -> error::Result<()> {
+            let query = format!(
+                "SELECT min_by({}, {}) FROM {}",
+                FLOAT64_COLUMN_NAME, STRING_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<f64, arrow::array::Float64Array>(df).await?;
+            assert_eq!(result, MIN_FLOAT_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_int_string() -> error::Result<()> {
+            let query = format!(
+                "SELECT min_by({}, {}) FROM {}",
+                INT64_COLUMN_NAME, STRING_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<i64, arrow::array::Int64Array>(df).await?;
+            assert_eq!(result, MIN_INT_VALUE);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_dictionary_int() -> error::Result<()> {
+            let query = format!(
+                "SELECT min_by({}, {}) FROM {}",
+                DICTIONARY_COLUMN_NAME, INT64_COLUMN_NAME, TEST_TABLE_NAME
+            );
+            let df = ctx()?.sql(&query).await?;
+            let result = extract_single_value::<String, arrow::array::StringArray>(df).await?;
+            assert_eq!(result, MIN_DICTIONARY_VALUE);
+            Ok(())
+        }
+
+        fn ctx() -> error::Result<prelude::SessionContext> {
+            let ctx = test_ctx()?;
+            let min_by_udaf = MinByFunction::new();
+            ctx.register_udaf(min_by_udaf.into());
+            Ok(ctx)
+        }
+    }
+}