如何使用laravel 5.2 Schema Builder创建唯一约束?
Schema::create('my_pivot', function(Blueprint $table){
$table->increments('id');
$table->integer('table1_id')->unsigned();
$table->integer('table2_id')->unsigned();
$table->foreign('table1_id')->references('id')->on('table1');
$table->foreign('table2_id')->references('id')->on('table2');
//Here i need to add an unique constraint to 'key1' + 'key2'
});