mysql随机取数_MySQL
- WBOYOriginal
- 2016-06-01 13:06:591097browse
order by RAND() 效率太差.
我的主键为string,网上的高效语句也无法用上.于是自己琢磨了个新的随机取数处理方法. 未做测试.先记录下.
第一步,获取将要获取的数量的总数量.
string hql_nums = "select COUNT(*) from Table where a='" + a+ "'"; int allnums = MysqlHibernate.GetInstance().getCout(hql_nums);
Random r = new Random(); int begin = r.Next(allnums - nums); //nums为需要取值数量.防止取数不够
第三步. 以begin为起点, 取2*nums 条数据.然后对数据进行排序.获取需要的nums条数据.
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