imported flash card

supabase/migrations/006_flashcard_list_hierarchy.sql

@@ -0,0 +1,20 @@
+-- ============================================
+-- MIGRATION: Add parent/child list support
+-- ============================================
+
+-- 'parent' = chứa child lists, 'term' = chứa terms
+ALTER TABLE flashcard_list
+    ADD COLUMN type VARCHAR(10) NOT NULL DEFAULT 'term';
+
+-- Self-referencing FK: null nếu là top-level list
+ALTER TABLE flashcard_list
+    ADD COLUMN parent_id INT REFERENCES flashcard_list(id) ON DELETE SET NULL;
+
+-- child_ids không cần column — query: SELECT id FROM flashcard_list WHERE parent_id = ?
+
+-- ============================================
+-- INDEXES
+-- ============================================
+
+CREATE INDEX idx_list_parent_id ON flashcard_list(parent_id);
+CREATE INDEX idx_list_type      ON flashcard_list(type);