某前台sql语句,简化后如下SELECT products_name,products_viewed FROM `products_description` ORDER BY products_viewed DESC,products_name LIMIT 0,20; 该语句经常大批量出现在慢日志中! 初步看改语句,非常简单,根据products_viewed(产品被查看次数)倒序排序,再根据products_name(产品名字)排序!在products_viewed和products_name
SELECT t0.ID as id, t0.`NAME` as name, t0.PHONE as phone, t0.`CITY_CODE` as cityCode, t0.SHOOTING_TIME as shootingTime, t0.REMARK as remark, t0.SOURCE_FROM as sourceFrom,-- 平台来源 t0.REFER as refer, t0.UPDATE_TIME as updateTime, CONCAT(IFNULL(t0.SHOOTI
摘要 IN 一定走索引吗?那当然了,不走索引还能全部扫描吗?好像之前有看到过什么Exist,IN走不走索引的讨论.但是好像看的太久了,又忘记了.哈哈,如果你也忘记了MySQL中IN是如何查询的,就来复习下吧. 问题 问题要从之前的统计店铺数关注人数说起 SELECT shop_id, count(user_Id) as attentionNumber FROM shop_attention WHERE shop_id IN <foreach collection="shopIds"
对于大量left join 的表查询,可以在关键的 连接节点字段上创建索引. 问题: 大量的left join 怎么优化 select a.id,a.num,b.num,b.pcs,c.num, c.pcs,d.num,d.pcs,e.num,e.pcs,a.x, a.y from a left join b.id=a.id and b.time=a.time left join c.id=a.id and b.time=a.time left join d.id=a.id and b.time