diff --git a/sql/migrations/000001_init.up.sql b/sql/migrations/000001_init.up.sql
index 0b7fa33..eba22e2 100644
--- a/sql/migrations/000001_init.up.sql
+++ b/sql/migrations/000001_init.up.sql
@@ -27,8 +27,8 @@ CREATE TABLE users (
     id                  bigint              GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
     avatar_id           bigint              REFERENCES images (id),
     passhash            text                NOT NULL,
-    mail                text                CHECK (mail ~ '[a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]+'),
-    nickname            text                NOT NULL CHECK (nickname ~ '^[a-zA-Z0-9_-]+$'),
+    mail                text                CHECK (mail ~ '^[a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]+$'),
+    nickname            text                UNIQUE NOT NULL CHECK (nickname ~ '^[a-zA-Z0-9_-]{3,}$'),
     disp_name           text,
     user_desc           text,
     creation_date       timestamptz         NOT NULL,