#方法一:使用 not in ,容易理解,效率低 ~执行时间为:1.395秒~
SELECT COUNT(1) FROM ecs_goods WHERE ecs_goods.goods_id NOT IN (SELECT ecs_member_price.goods_id FROM ecs_member_price);
#方法二:使用 left join...on... , "B.ID isnull" 表示左连接之后在B.ID 字段为 null的记录 ~执行时间:0.739秒~
SELECT COUNT(1) FROM ecs_goods LEFT JOIN ecs_member_price ON ecs_goods.goods_id=ecs_member_price.goods_id WHERE ecs_member_price.goods_id IS NULL;
#方法三:逻辑相对复杂,但是速度最快 ~执行时间: 0.570秒~
SELECT COUNT(1) FROM ecs_goods c WHERE (SELECT COUNT(1) AS num FROM ecs_member_price WHERE ecs_member_price.goods_id=ecs_goods.goods_id) = 0;
在thinkphp中可以这样来写
$data = Db::name('article') ->field('article_id,article_title') ->where('article_cate_id',$cate_id) ->where('( select COUNT(1) AS num from news where news.news_article_id = article.article_id ) = 0') ->order('article_time desc') ->paginate(10,false,['query'=>request()->param()]);