diff --git a/database/migrations/2020_02_22_164304_add_unique_constraint_to_tag_relations.php b/database/migrations/2020_02_22_164304_add_unique_constraint_to_tag_relations.php
new file mode 100644
index 0000000..b8d6f50
--- /dev/null
+++ b/database/migrations/2020_02_22_164304_add_unique_constraint_to_tag_relations.php
@@ -0,0 +1,38 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class AddUniqueConstraintToTagRelations extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('ejaculation_tag', function (Blueprint $table) {
+            $table->unique(['ejaculation_id', 'tag_id']);
+        });
+        Schema::table('metadata_tag', function (Blueprint $table) {
+            $table->unique(['metadata_url', 'tag_id']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('ejaculation_tag', function (Blueprint $table) {
+            $table->dropUnique(['ejaculation_id', 'tag_id']);
+        });
+        Schema::table('metadata_tag', function (Blueprint $table) {
+            $table->dropUnique(['metadata_url', 'tag_id']);
+        });
+    }
+}