添加外键约束

+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class WorkOrderLogsAddForeignId extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+       Schema::table('gl_work_order_logs', function (Blueprint $table) {
+           // 字段已存在，给字段添加外键约束
+           $table->foreign('work_order_id')
+               ->references('id')->on('gl_work_orders')
+               ->onDelete('cascade'); // 设置级联删除
+       });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('gl_work_order_logs', function (Blueprint $table) {
+            // 删除外键约束
+            $table->dropForeign(['work_order_id']);
+        });
+    }
+}