clicks are deleted when connected links are

fixes #7

migrations/20210401070030_on_delete_cascade.sql

@@ -0,0 +1,24 @@
+-- Add migration script here
+PRAGMA foreign_keys = off;
+
+
+CREATE TABLE new_clicks (
+    id INTEGER PRIMARY KEY NOT NULL,
+    link INT NOT NULL,
+    created_at TIMESTAMP NOT NULL,
+    FOREIGN KEY (link) REFERENCES links (id) ON DELETE CASCADE
+);
+
+INSERT INTO
+    new_clicks
+SELECT
+    *
+FROM
+    clicks;
+
+
+DROP TABLE clicks;
+ALTER TABLE
+    new_clicks RENAME TO clicks;
+    
+PRAGMA foreign_keys = on;