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mysql Count DistinCt

count(distinct s_number)

Distinct可以转化为GROUP BY,大多数情况下GROUP BY的效率要高于DICTINCT,参考下这个问题:mysql如何优化大数据量情况下的distinct!

SELECT COUNT(1) FROM customer_ProviderUser cp WHERE cp.providerUserType=4 AND cp.ownerId='0a84c0f359b933a3f8ab3e8bd2633e91' AND cp.ownerType=1 AND cp.provider=2 AND providerUserId IN ( SELECT providerUserId FROM search_Result W...

1. 把你的day字段类型改为long型,在页面显示的时候在格式化成自己需要的样式; 2. 在day字段上建立索引; 3. 把ip_4表类型有InnoDB改为MyISAM,如果不需要事物支持的话,建议不要使用InnoDB。

select count(*) from p_score_sx_zhishanglihepiao21024 a where user_id in (SELECT user_id, COUNT(*) AS cnt FROM p_score_sx_zhishanglihepiao21024 WHERE create_dt LIKE '2010-05-06%' GROUP BY user_id HAVING cnt >= 100) 就是效率低了...

db.log.group({key:{time:1},cond:{},reduce:function(curr,result){if(result.arr.indexOf(curr.username)==-1){result.arr.push(curr.username);result.count++;}},initial:{arr:[],count:0}}); 在本地验证过,initial方法初始化每个group结果...

select city,count(*) from user group by city 用这个分组函数就可以统计

select ip,spare2, count(distinct concat(ip,pc)) from user group by ip

1.where字段的索引。 2.建议查询增加上一个datetime范围。

1. count不重复的记录条数 SELECT COUNT(DISTINCT id) FROM tablename; 2. 需要返回记录不同的id的具体值 SELECT DISTINCT id FROM tablename; 3. 上面的情况2对于需要返回mysql表中2列以上的结果时会有歧义 比如 SELECT DISTINCT id,type ...

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