fix: set transaction mode in single command (#2450)

src/driver/sqlx_mysql.rs

@@ -275,18 +275,19 @@ pub(crate) async fn set_transaction_config(
     isolation_level: Option<IsolationLevel>,
     access_mode: Option<AccessMode>,
 ) -> Result<(), DbErr> {
+    let mut settings = Vec::new();
+
     if let Some(isolation_level) = isolation_level {
-        let stmt = Statement {
-            sql: format!("SET TRANSACTION ISOLATION LEVEL {isolation_level}"),
-            values: None,
-            db_backend: DbBackend::MySql,
-        };
-        let query = sqlx_query(&stmt);
-        conn.execute(query).await.map_err(sqlx_error_to_exec_err)?;
+        settings.push(format!("ISOLATION LEVEL {isolation_level}"));
     }
+
     if let Some(access_mode) = access_mode {
+        settings.push(access_mode.to_string());
+    }
+
+    if !settings.is_empty() {
         let stmt = Statement {
-            sql: format!("SET TRANSACTION {access_mode}"),
+            sql: format!("SET TRANSACTION {}", settings.join(", ")),
             values: None,
             db_backend: DbBackend::MySql,
         };