Bug Report: Duplicate `ORDER BY` causes SQLSTATE\[42000] on SQL Server

[phongle8912]

Plugin: RainLab.Blog
OctoberCMS Version: 3.7.12
RainLab.Blog Version: 1.7.1
Database: SQL Server (tested with ODBC Driver 17)

---

❗ Description

When using the Blog Post Import feature, after uploading the import file, the system throws the following SQL error on Microsoft SQL Server:

SQLSTATE[42000]: [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]A column has been specified more than once in the order by list. Columns in the order by list must be unique.

Generated SQL query (excerpt):

... ORDER BY [sort_order] ASC, [system_files].[sort_order] ASC

This indicates that the query includes sort_order twice in the ORDER BY clause, which is not allowed on SQL Server.

---

🧪 Steps to Reproduce

1. Navigate to Blog > Import Posts in the backend.
2. Upload any valid import file.
3. Observe the error triggered by duplicate ORDER BY clauses.

---

📌 Notes

• This issue does not occur on MySQL, which silently ignores duplicate columns in the ORDER BY clause.
• Only affects Microsoft SQL Server, which enforces strict uniqueness on column names in ORDER BY.
• The error likely originates from the internal query used by the attachMany + deferred_bindings relationship in PostImport model.

---

✅ Suggested Fix

Ensure that ORDER BY clauses generated for file attachments remove duplicate column names when querying deferred bindings.

---