-- One-off migration: adds a description column to the charges table so a
-- manually-added charge (student profile → "+ Начисление") can carry a
-- short note explaining what it's for. Charges created by the daily
-- billing cron (cron/charge_students.php) leave it NULL.
--
-- IMPORTANT: this file contains Cyrillic text in its comments only, but
-- if you ever add Cyrillic to the migration itself, force the client to
-- utf8mb4 the same way scripts/add_category_to_expenses.sql documents.
--
-- MySQL doesn't support IF NOT EXISTS on ADD COLUMN — safe to run once;
-- re-running will error with "Duplicate column name", which is harmless.

ALTER TABLE charges ADD COLUMN description VARCHAR(255) NULL AFTER amount;
