feat(function): Add support for GREATEST / LEAST function (#844)

Signed-off-by: MATILLAT Quentin <[email protected]>

src/backend/query_builder.rs

@@ -666,6 +666,8 @@ pub trait QueryBuilder:
                     Function::Coalesce => "COALESCE",
                     Function::Count => "COUNT",
                     Function::IfNull => self.if_null_function(),
+                    Function::Greatest => self.greatest_function(),
+                    Function::Least => self.least_function(),
                     Function::CharLength => self.char_length_function(),
                     Function::Cast => "CAST",
                     Function::Lower => "LOWER",
@@ -1459,6 +1461,18 @@ pub trait QueryBuilder:
         "IFNULL"
     }
 
+    #[doc(hidden)]
+    /// The name of the function that represents the "greatest" function.
+    fn greatest_function(&self) -> &str {
+        "GREATEST"
+    }
+
+    #[doc(hidden)]
+    /// The name of the function that represents the "least" function.
+    fn least_function(&self) -> &str {
+        "LEAST"
+    }
+
     #[doc(hidden)]
     /// The name of the function that returns the char length.
     fn char_length_function(&self) -> &str {

src/backend/sqlite/query.rs

@@ -76,6 +76,14 @@ impl QueryBuilder for SqliteQueryBuilder {
         sql.push_param(value.clone(), self as _);
     }
 
+    fn greatest_function(&self) -> &str {
+        "MAX"
+    }
+
+    fn least_function(&self) -> &str {
+        "MIN"
+    }
+
     fn char_length_function(&self) -> &str {
         "LENGTH"
     }

src/func.rs

@@ -15,6 +15,8 @@ pub enum Function {
     Abs,
     Count,
     IfNull,
+    Greatest,
+    Least,
     CharLength,
     Cast,
     Custom(DynIden),
@@ -392,6 +394,76 @@ impl Func {
         FunctionCall::new(Function::CharLength).arg(expr)
     }
 
+    /// Call `GREATEST` function.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use sea_query::{tests_cfg::*, *};
+    ///
+    /// let query = Query::select()
+    ///     .expr(Func::greatest([
+    ///         Expr::col(Char::SizeW).into(),
+    ///         Expr::col(Char::SizeH).into(),
+    ///     ]))
+    ///     .from(Char::Table)
+    ///     .to_owned();
+    ///
+    /// assert_eq!(
+    ///     query.to_string(MysqlQueryBuilder),
+    ///     r#"SELECT GREATEST(`size_w`, `size_h`) FROM `character`"#
+    /// );
+    /// assert_eq!(
+    ///     query.to_string(PostgresQueryBuilder),
+    ///     r#"SELECT GREATEST("size_w", "size_h") FROM "character""#
+    /// );
+    /// assert_eq!(
+    ///     query.to_string(SqliteQueryBuilder),
+    ///     r#"SELECT MAX("size_w", "size_h") FROM "character""#
+    /// );
+    /// ```
+    pub fn greatest<I>(args: I) -> FunctionCall
+    where
+        I: IntoIterator<Item = SimpleExpr>,
+    {
+        FunctionCall::new(Function::Greatest).args(args)
+    }
+
+    /// Call `LEAST` function.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use sea_query::{tests_cfg::*, *};
+    ///
+    /// let query = Query::select()
+    ///     .expr(Func::least([
+    ///         Expr::col(Char::SizeW).into(),
+    ///         Expr::col(Char::SizeH).into(),
+    ///     ]))
+    ///     .from(Char::Table)
+    ///     .to_owned();
+    ///
+    /// assert_eq!(
+    ///     query.to_string(MysqlQueryBuilder),
+    ///     r#"SELECT LEAST(`size_w`, `size_h`) FROM `character`"#
+    /// );
+    /// assert_eq!(
+    ///     query.to_string(PostgresQueryBuilder),
+    ///     r#"SELECT LEAST("size_w", "size_h") FROM "character""#
+    /// );
+    /// assert_eq!(
+    ///     query.to_string(SqliteQueryBuilder),
+    ///     r#"SELECT MIN("size_w", "size_h") FROM "character""#
+    /// );
+    /// ```
+    pub fn least<I>(args: I) -> FunctionCall
+    where
+        I: IntoIterator<Item = SimpleExpr>,
+    {
+        FunctionCall::new(Function::Least).args(args)
+    }
+
     /// Call `IF NULL` function.
     ///
     /// # Examples