Add select APIs

examples/sqlx-mysql/src/main.rs

@@ -104,22 +104,12 @@ async fn count_fruits_by_cake(db: &Database) -> Result<(), QueryErr> {
 
     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 select = cake::Entity::find()
+        .left_join(cake::Relation::Fruit)
+        .clear_selects()
+        .column(cake::Column::Name)
+        .expr_as(fruit::Column::Id.count(), "num_of_fruits")
+        .group_by(cake::Column::Name);
 
     let results = select.into_model::<SelectResult>().all(db).await?;
 

src/entity/column.rs

@@ -15,6 +15,27 @@ macro_rules! bind_oper {
     };
 }
 
+macro_rules! bind_agg_func {
+    ( $func: ident ) => {
+        fn $func(&self) -> SimpleExpr {
+            Expr::tbl(self.entity_name(), *self).$func()
+        }
+    };
+}
+
+macro_rules! bind_vec_func {
+    ( $func: ident ) => {
+        #[allow(clippy::wrong_self_convention)]
+        fn $func<V, I>(&self, v: I) -> SimpleExpr
+        where
+            V: Into<Value>,
+            I: IntoIterator<Item = V>,
+        {
+            Expr::tbl(self.entity_name(), *self).$func(v)
+        }
+    };
+}
+
 pub trait ColumnTrait: IdenStatic {
     type EntityName: EntityName;
 
@@ -24,6 +45,10 @@ pub trait ColumnTrait: IdenStatic {
         Rc::new(Self::EntityName::default()) as Rc<dyn Iden>
     }
 
+    fn as_column_ref(&self) -> (Rc<dyn Iden>, Rc<dyn Iden>) {
+        (self.entity_name(), Rc::new(*self) as Rc<dyn Iden>)
+    }
+
     bind_oper!(eq);
     bind_oper!(ne);
     bind_oper!(gt);
@@ -144,4 +169,19 @@ pub trait ColumnTrait: IdenStatic {
         let pattern = format!("%{}%", s);
         Expr::tbl(self.entity_name(), *self).like(&pattern)
     }
-}
+
+    bind_agg_func!(max);
+    bind_agg_func!(min);
+    bind_agg_func!(sum);
+    bind_agg_func!(count);
+
+    fn if_null<V>(&self, v: V) -> SimpleExpr
+    where
+        V: Into<Value>,
+    {
+        Expr::tbl(self.entity_name(), *self).if_null(v)
+    }
+
+    bind_vec_func!(is_in);
+    bind_vec_func!(is_not_in);
+}

src/query/select.rs

@@ -1,11 +1,13 @@
 use crate::{
-    EntityTrait, Identity, Iterable, PrimaryKeyOfModel, Related, RelationDef, RelationTrait,
-    Statement,
+    ColumnTrait, EntityTrait, Identity, Iterable, ModelTrait, PrimaryKeyOfModel, Related,
+    RelationDef, RelationTrait, Statement,
 };
 use core::fmt::Debug;
 use core::marker::PhantomData;
 pub use sea_query::JoinType;
-use sea_query::{Expr, Iden, IntoIden, Order, QueryBuilder, SelectStatement, SimpleExpr};
+use sea_query::{
+    Alias, Expr, Iden, IntoIden, Order, QueryBuilder, SelectExpr, SelectStatement, SimpleExpr,
+};
 use std::rc::Rc;
 
 #[derive(Clone, Debug)]
@@ -74,6 +76,72 @@ where
         self
     }
 
+    pub fn clear_selects(mut self) -> Self {
+        self.query.clear_selects();
+        self
+    }
+
+    /// ```
+    /// use sea_orm::{ColumnTrait, EntityTrait, tests_cfg::cake, sea_query::PostgresQueryBuilder};
+    ///
+    /// assert_eq!(
+    ///     cake::Entity::find()
+    ///         .clear_selects()
+    ///         .column(cake::Column::Name)
+    ///         .build(PostgresQueryBuilder)
+    ///         .to_string(),
+    ///     r#"SELECT "cake"."name" FROM "cake""#
+    /// );
+    /// ```
+    pub fn column<C>(mut self, col: C) -> Self
+    where
+        C: ColumnTrait,
+    {
+        self.query.column(col.as_column_ref());
+        self
+    }
+
+    /// ```
+    /// use sea_orm::{ColumnTrait, EntityTrait, tests_cfg::cake, sea_query::PostgresQueryBuilder};
+    ///
+    /// assert_eq!(
+    ///     cake::Entity::find()
+    ///         .clear_selects()
+    ///         .column(cake::Column::Name)
+    ///         .group_by(cake::Column::Name)
+    ///         .build(PostgresQueryBuilder)
+    ///         .to_string(),
+    ///     r#"SELECT "cake"."name" FROM "cake" GROUP BY "cake"."name""#
+    /// );
+    /// ```
+    pub fn group_by<C>(mut self, col: C) -> Self
+    where
+        C: ColumnTrait,
+    {
+        self.query.group_by_col(col.as_column_ref());
+        self
+    }
+
+    /// ```
+    /// use sea_orm::{ColumnTrait, EntityTrait, tests_cfg::cake, sea_query::PostgresQueryBuilder};
+    ///
+    /// assert_eq!(
+    ///     cake::Entity::find()
+    ///         .clear_selects()
+    ///         .expr_as(cake::Column::Id.count(), "count")
+    ///         .build(PostgresQueryBuilder)
+    ///         .to_string(),
+    ///     r#"SELECT COUNT("cake"."id") AS "count" FROM "cake""#
+    /// );
+    /// ```
+    pub fn expr_as(mut self, expr: SimpleExpr, alias: &str) -> Self {
+        self.query.expr(SelectExpr {
+            expr,
+            alias: Some(Rc::new(Alias::new(alias))),
+        });
+        self
+    }
+
     /// ```
     /// use sea_orm::{ColumnTrait, EntityTrait, tests_cfg::cake, sea_query::MysqlQueryBuilder};
     ///
@@ -95,8 +163,6 @@ where
         R: EntityTrait + Related<E>,
         R::PrimaryKey: PrimaryKeyOfModel<R::Model>,
     {
-        use crate::{ColumnTrait, ModelTrait};
-
         if let Some(key) = R::PrimaryKey::iter().next() {
             // TODO: supporting composite primary key
             let col = key.into_column();