Example

examples/sqlx-mysql/Readme.md

@@ -32,4 +32,10 @@ find models belong to: SELECT `fruit`.`id`, `fruit`.`name`, `fruit`.`cake_id` FR
 Model { id: 1, name: "Blueberry", cake_id: Some(1) }
 
 Model { id: 2, name: "Rasberry", cake_id: Some(1) }
+
+count fruits by cake: SELECT `cake`.`name`, COUNT(`fruit`.`id`) AS `num_of_fruits` FROM `cake` LEFT JOIN `fruit` ON `cake`.`id` = `fruit`.`cake_id` GROUP BY `cake`.`name`
+
+SelectResult { name: "New York Cheese", num_of_fruits: 2 }
+
+SelectResult { name: "Chocolate Fudge", num_of_fruits: 1 }
 ```

examples/sqlx-mysql/src/main.rs

@@ -52,4 +52,55 @@ async fn main() {
         println!("{:?}", ff);
         println!();
     }
+
+    count_fruits_by_cake(&db).await;
+}
+
+async fn count_fruits_by_cake(db: &Database) {
+    #[derive(Debug)]
+    struct SelectResult {
+        name: String,
+        num_of_fruits: i32,
+    }
+
+    {
+        // TODO: implement with derive macro
+        use sea_orm::{FromQueryResult, QueryResult, TypeErr};
+
+        impl FromQueryResult for SelectResult {
+            fn from_query_result(row: QueryResult) -> Result<Self, TypeErr> {
+                Ok(Self {
+                    name: row.try_get("name")?,
+                    num_of_fruits: row.try_get("num_of_fruits")?,
+                })
+            }
+        }
+    }
+
+    print!("count fruits by cake: ");
+
+    let mut select = cake::Entity::find().left_join(cake::Relation::Fruit);
+    {
+        use sea_orm::sea_query::*;
+        type Cake = cake::Column;
+        type Fruit = fruit::Column;
+
+        select
+            .query()
+            .clear_selects()
+            .column((cake::Entity, Cake::Name))
+            .expr_as(
+                Expr::tbl(fruit::Entity, Fruit::Id).count(),
+                Alias::new("num_of_fruits"),
+            )
+            .group_by_col((cake::Entity, Cake::Name));
+    }
+
+    let results = select.into_model::<SelectResult>().all(db).await.unwrap();
+
+    println!();
+    for rr in results.iter() {
+        println!("{:?}", rr);
+        println!();
+    }
 }