diff --git a/src/main/resources/scripts/V3_3_0_1__add_user_account_name.sql b/src/main/resources/scripts/V3_3_0_1__add_user_account_name.sql
index 8d5881fc..0ae164ec 100644
--- a/src/main/resources/scripts/V3_3_0_1__add_user_account_name.sql
+++ b/src/main/resources/scripts/V3_3_0_1__add_user_account_name.sql
@@ -1 +1,7 @@
-ALTER TABLE users ADD COLUMN account_name VARCHAR(63) NOT NULL UNIQUE;
\ No newline at end of file
+ALTER TABLE users ADD COLUMN account_name VARCHAR(63);
+
+UPDATE users SET account_name = SUBSTRING(mail FROM 1 FOR POSITION('@' IN mail) - 1);
+
+ALTER TABLE users ALTER COLUMN account_name SET NOT NULL;
+
+CREATE UNIQUE INDEX users_account_name_index ON users (account_name);
\ No newline at end of file