Try

src/database/db_connection.rs

@@ -230,26 +230,55 @@ impl<'a> ConnectionTrait<'a> for DatabaseConnection {
             #[cfg(feature = "sqlx-mysql")]
             DatabaseConnection::SqlxMySqlPoolConnection {
                 support_returning, ..
-            } => *support_returning,
+            } => {
+                // Supported if it's MariaDB on or after version 10.5.0
+                // Not supported in all MySQL versions
+                *support_returning
+            }
             #[cfg(feature = "sqlx-postgres")]
-            DatabaseConnection::SqlxPostgresPoolConnection(_) => true,
+            DatabaseConnection::SqlxPostgresPoolConnection(_) => {
+                // Supported by all Postgres versions
+                true
+            }
             #[cfg(feature = "sqlx-sqlite")]
-            DatabaseConnection::SqlxSqlitePoolConnection(_) => false,
+            DatabaseConnection::SqlxSqlitePoolConnection(_) => {
+                // Supported by SQLite on or after version 3.35.0 (2021-03-12)
+                false
+            }
+            #[cfg(feature = "mock")]
+            DatabaseConnection::MockDatabaseConnection(conn) => match conn.get_database_backend() {
+                DbBackend::MySql => false,
+                DbBackend::Postgres => true,
+                DbBackend::Sqlite => false,
+            },
             DatabaseConnection::Disconnected => panic!("Disconnected"),
-            _ => unimplemented!(),
         }
     }
 
     fn returning_on_update(&self) -> bool {
         match self {
             #[cfg(feature = "sqlx-mysql")]
-            DatabaseConnection::SqlxMySqlPoolConnection { .. } => false,
+            DatabaseConnection::SqlxMySqlPoolConnection { .. } => {
+                // Not supported in all MySQL & MariaDB versions
+                false
+            }
             #[cfg(feature = "sqlx-postgres")]
-            DatabaseConnection::SqlxPostgresPoolConnection(_) => true,
+            DatabaseConnection::SqlxPostgresPoolConnection(_) => {
+                // Supported by all Postgres versions
+                true
+            }
             #[cfg(feature = "sqlx-sqlite")]
-            DatabaseConnection::SqlxSqlitePoolConnection(_) => false,
+            DatabaseConnection::SqlxSqlitePoolConnection(_) => {
+                // Supported by SQLite on or after version 3.35.0 (2021-03-12)
+                false
+            }
+            #[cfg(feature = "mock")]
+            DatabaseConnection::MockDatabaseConnection(conn) => match conn.get_database_backend() {
+                DbBackend::MySql => false,
+                DbBackend::Postgres => true,
+                DbBackend::Sqlite => false,
+            },
             DatabaseConnection::Disconnected => panic!("Disconnected"),
-            _ => unimplemented!(),
         }
     }
 

src/driver/sqlx_mysql.rs

@@ -195,6 +195,7 @@ async fn into_db_connection(pool: MySqlPool) -> Result<DatabaseConnection, DbErr
         let version: String = query_result.try_get("", "Value")?;
         let support_returning = if !version.contains("MariaDB") {
             // This is MySQL
+            // Not supported in all MySQL versions
             false
         } else {
             // This is MariaDB
@@ -212,6 +213,7 @@ async fn into_db_connection(pool: MySqlPool) -> Result<DatabaseConnection, DbErr
             }
             let ver_major = parse_captures!(1);
             let ver_minor = parse_captures!(2);
+            // Supported if it's MariaDB with version 10.5.0 or after
             ver_major >= 10 && ver_minor >= 5
         };
         (version, support_returning)

tests/returning_tests.rs

@@ -31,7 +31,7 @@ async fn main() -> Result<(), DbErr> {
             (Column::ProfitMargin, 0.5.into()),
         ])
         .and_where(Column::Id.eq(1));
-    
+
     let mut returning = Query::select();
     returning.columns(vec![Column::Id, Column::Name, Column::ProfitMargin]);
     if db.returning_on_insert() {
@@ -43,8 +43,18 @@ async fn main() -> Result<(), DbErr> {
 
     create_tables(db).await?;
     println!("db_version: {:#?}", db.version());
-    db.query_one(builder.build(&insert)).await?;
-    db.query_one(builder.build(&update)).await?;
+    let insert_res = db.query_one(builder.build(&insert)).await?.expect("Insert failed");
+    if db.returning_on_insert() {
+        let _id: i32 = insert_res.try_get("", "id")?;
+        let _name: String = insert_res.try_get("", "name")?;
+        let _profit_margin: f64 = insert_res.try_get("", "profit_margin")?;
+    }
+    let update_res = db.query_one(builder.build(&update)).await?.expect("Update filed");
+    if db.returning_on_update() {
+        let _id: i32 = insert_res.try_get("", "id")?;
+        let _name: String = insert_res.try_get("", "name")?;
+        let _profit_margin: f64 = insert_res.try_get("", "profit_margin")?;
+    }
     ctx.delete().await;
 
     Ok(())