-- ==============================================================================
-- RailwaySystem 数据库 V2 回滚脚本: 001_rollback_new_tables.sql
-- 适用数据库: KingbaseES V009R003C018 (schema: public)
-- 执行目标: 安全下线并删除数据库 V2 新增的 8 张培训业务表
-- 事务边界: 全程在显式事务 BEGIN ... COMMIT 中执行
-- 说明: 先显式解除外键约束，然后按依赖反序执行常规 DROP TABLE (无 CASCADE)
-- ==============================================================================

BEGIN;

-- 步骤 1: 显式解除 V2 新增表之间的外键约束
ALTER TABLE train_student_score DROP CONSTRAINT IF EXISTS fk_score_enrollment;
ALTER TABLE train_student_score DROP CONSTRAINT IF EXISTS fk_score_item;

ALTER TABLE train_score_item DROP CONSTRAINT IF EXISTS fk_scoreitem_plan;
ALTER TABLE train_score_item DROP CONSTRAINT IF EXISTS fk_scoreitem_plancourse;

ALTER TABLE train_lesson DROP CONSTRAINT IF EXISTS fk_lesson_plancourse;
ALTER TABLE train_lesson DROP CONSTRAINT IF EXISTS fk_lesson_teacher;
ALTER TABLE train_lesson DROP CONSTRAINT IF EXISTS fk_lesson_classroom;
ALTER TABLE train_lesson DROP CONSTRAINT IF EXISTS fk_lesson_site;

ALTER TABLE train_accommodation DROP CONSTRAINT IF EXISTS fk_accomm_enrollment;
ALTER TABLE train_accommodation DROP CONSTRAINT IF EXISTS fk_accomm_dorm;

ALTER TABLE train_enrollment DROP CONSTRAINT IF EXISTS fk_enrollment_plan;
ALTER TABLE train_enrollment DROP CONSTRAINT IF EXISTS fk_enrollment_student;

ALTER TABLE train_plan_course DROP CONSTRAINT IF EXISTS fk_plancourse_plan;
ALTER TABLE train_plan_course DROP CONSTRAINT IF EXISTS fk_plancourse_course;

ALTER TABLE train_course_resource DROP CONSTRAINT IF EXISTS fk_cr_course;
ALTER TABLE train_course_resource DROP CONSTRAINT IF EXISTS fk_cr_resource;

-- 步骤 2: 按依赖拓扑反序执行常规 DROP TABLE
DROP TABLE IF EXISTS train_student_score;
DROP TABLE IF EXISTS train_score_item;
DROP TABLE IF EXISTS train_lesson;
DROP TABLE IF EXISTS train_accommodation;
DROP TABLE IF EXISTS train_enrollment;
DROP TABLE IF EXISTS train_plan_course;
DROP TABLE IF EXISTS train_course_resource;
DROP TABLE IF EXISTS train_resource;

COMMIT;