diff --git a/packages/backend/server/migrations/20240819100204_editor_record/migration.sql b/packages/backend/server/migrations/20240826033024_editor_record/migration.sql
similarity index 78%
rename from packages/backend/server/migrations/20240819100204_editor_record/migration.sql
rename to packages/backend/server/migrations/20240826033024_editor_record/migration.sql
index 143ab9e23f..13b0e31617 100644
--- a/packages/backend/server/migrations/20240819100204_editor_record/migration.sql
+++ b/packages/backend/server/migrations/20240826033024_editor_record/migration.sql
@@ -6,7 +6,7 @@ ALTER TABLE "snapshots" ADD COLUMN     "created_by" VARCHAR,
 ADD COLUMN     "updated_by" VARCHAR;
 
 -- AlterTable
-ALTER TABLE "updates" ADD COLUMN     "created_by" VARCHAR NOT NULL DEFAULT 'system';
+ALTER TABLE "updates" ADD COLUMN     "created_by" VARCHAR DEFAULT 'system';
 
 -- AddForeignKey
 ALTER TABLE "snapshots" ADD CONSTRAINT "snapshots_created_by_fkey" FOREIGN KEY ("created_by") REFERENCES "users"("id") ON DELETE SET NULL ON UPDATE CASCADE;
@@ -15,7 +15,7 @@ ALTER TABLE "snapshots" ADD CONSTRAINT "snapshots_created_by_fkey" FOREIGN KEY (
 ALTER TABLE "snapshots" ADD CONSTRAINT "snapshots_updated_by_fkey" FOREIGN KEY ("updated_by") REFERENCES "users"("id") ON DELETE SET NULL ON UPDATE CASCADE;
 
 -- AddForeignKey
-ALTER TABLE "updates" ADD CONSTRAINT "updates_created_by_fkey" FOREIGN KEY ("created_by") REFERENCES "users"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "updates" ADD CONSTRAINT "updates_created_by_fkey" FOREIGN KEY ("created_by") REFERENCES "users"("id") ON DELETE SET NULL ON UPDATE CASCADE;
 
 -- AddForeignKey
-ALTER TABLE "snapshot_histories" ADD CONSTRAINT "snapshot_histories_created_by_fkey" FOREIGN KEY ("created_by") REFERENCES "users"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "snapshot_histories" ADD CONSTRAINT "snapshot_histories_created_by_fkey" FOREIGN KEY ("created_by") REFERENCES "users"("id") ON DELETE SET NULL ON UPDATE CASCADE;
diff --git a/packages/backend/server/schema.prisma b/packages/backend/server/schema.prisma
index 20ce000960..ecfa90f290 100644
--- a/packages/backend/server/schema.prisma
+++ b/packages/backend/server/schema.prisma
@@ -286,10 +286,10 @@ model Update {
   blob        Bytes    @db.ByteA
   createdAt   DateTime @map("created_at") @db.Timestamptz(3)
   // TODO(@darkskygit): fullfill old update, remove default value in next release
-  createdBy   String   @map("created_by") @db.VarChar @default("system")
+  createdBy   String?  @default("system") @map("created_by") @db.VarChar
 
   // delete update if createor's account is deleted
-  createdByUser User @relation(name: "createdUpdate", fields: [createdBy], references: [id], onDelete: Cascade)
+  createdByUser User? @relation(name: "createdUpdate", fields: [createdBy], references: [id], onDelete: SetNull)
 
   // @deprecated use createdAt only
   seq Int? @db.Integer
@@ -308,7 +308,7 @@ model SnapshotHistory {
   createdBy   String?  @map("created_by") @db.VarChar
 
   // delete history if creator's account is deleted
-  createdByUser User? @relation(name: "createdHistory", fields: [createdBy], references: [id], onDelete: Cascade)
+  createdByUser User? @relation(name: "createdHistory", fields: [createdBy], references: [id], onDelete: SetNull)
 
   @@id([workspaceId, id, timestamp])
   @@map("snapshot_histories")