diff --git a/migrations/mysql/0019_users_user_unique.up.sql b/migrations/mysql/0019_users_user_unique.up.sql
new file mode 100644
index 0000000..bfc970f
--- /dev/null
+++ b/migrations/mysql/0019_users_user_unique.up.sql
@@ -0,0 +1 @@
+ALTER TABLE users ADD CONSTRAINT user_unique UNIQUE (user);
\ No newline at end of file