diff --git a/src/models/mod.rs b/src/models/mod.rs
index 3dbe65b..3384493 100644
--- a/src/models/mod.rs
+++ b/src/models/mod.rs
@@ -37,10 +37,11 @@ pub struct ListParams {
 }
 
 impl ListParams {
-    pub fn get_order_by(&self) -> String {
-        let default_order_by = "updated_at".to_string();
-        let order_by = self.order_by.as_ref().unwrap_or(&default_order_by);
-        let order = self.order.as_ref().unwrap_or(&Order::Desc);
-        format!("{} {}", order_by, order)
+    pub fn get_order_by(&self) -> Option<String> {
+        if let Some(order_by) = self.order_by.as_ref() {
+            let order = self.order.as_ref().unwrap_or(&Order::Desc);
+            return Some(format!("{} {}", order_by, order));
+        }
+        None
     }
 }
diff --git a/src/models/owner.rs b/src/models/owner.rs
index 0825192..8c2f3fd 100644
--- a/src/models/owner.rs
+++ b/src/models/owner.rs
@@ -62,18 +62,31 @@ impl Model for Owner {
 
     async fn list(db: &PgPool, list_params: ListParams) -> Result<Vec<Self>> {
         let timer = std::time::Instant::now();
-        let result = sqlx::query_as!(
-            Self,
-            "SELECT * FROM owners
-            ORDER BY $1
-            LIMIT $2
-            OFFSET $3",
-            list_params.get_order_by(),
-            list_params.limit.unwrap_or(10),
-            list_params.offset.unwrap_or(0),
-        )
-        .fetch_all(db)
-        .await?;
+        let result = if let Some(order_by) = list_params.get_order_by() {
+            sqlx::query_as!(
+                Self,
+                "SELECT * FROM owners
+                ORDER BY $1
+                LIMIT $2
+                OFFSET $3",
+                order_by,
+                list_params.limit.unwrap_or(10),
+                list_params.offset.unwrap_or(0),
+            )
+            .fetch_all(db)
+            .await?
+        } else {
+            sqlx::query_as!(
+                Self,
+                "SELECT * FROM owners
+                LIMIT $1
+                OFFSET $2",
+                list_params.limit.unwrap_or(10),
+                list_params.offset.unwrap_or(0),
+            )
+            .fetch_all(db)
+            .await?
+        };
         let elapsed = timer.elapsed();
         debug!("SELECT * FROM owners ... {:.3?}", elapsed);
         Ok(result)
diff --git a/src/models/shop.rs b/src/models/shop.rs
index ca3c0a3..c5203ca 100644
--- a/src/models/shop.rs
+++ b/src/models/shop.rs
@@ -67,18 +67,31 @@ impl Model for Shop {
 
     async fn list(db: &PgPool, list_params: ListParams) -> Result<Vec<Self>> {
         let timer = std::time::Instant::now();
-        let result = sqlx::query_as!(
-            Self,
-            "SELECT * FROM shops
-            ORDER BY $1
-            LIMIT $2
-            OFFSET $3",
-            list_params.get_order_by(),
-            list_params.limit.unwrap_or(10),
-            list_params.offset.unwrap_or(0),
-        )
-        .fetch_all(db)
-        .await?;
+        let result = if let Some(order_by) = list_params.get_order_by() {
+            sqlx::query_as!(
+                Self,
+                "SELECT * FROM shops
+                ORDER BY $1
+                LIMIT $2
+                OFFSET $3",
+                order_by,
+                list_params.limit.unwrap_or(10),
+                list_params.offset.unwrap_or(0),
+            )
+            .fetch_all(db)
+            .await?
+        } else {
+            sqlx::query_as!(
+                Self,
+                "SELECT * FROM shops
+                LIMIT $1
+                OFFSET $2",
+                list_params.limit.unwrap_or(10),
+                list_params.offset.unwrap_or(0),
+            )
+            .fetch_all(db)
+            .await?
+        };
         let elapsed = timer.elapsed();
         debug!("SELECT * FROM shops ... {:.3?}", elapsed);
         Ok(result)