Question

我想从基于费率字段的数据库中按百分比获取数据，我也想随机显示数据所以我试过这个

string sql = "(SELECT TOP 100 PERCENT * FROM tbl_adv WHERE Stars = 7 ORDER BY Rnd(-(1000*adID)*Time())) UNION (SELECT TOP 84 PERCENT * FROM tbl_adv WHERE Stars = 6 ORDER BY Rnd(-(1000*adID)*Time())) UNION (SELECT TOP 72 PERCENT * FROM tbl_adv WHERE Stars = 5 ORDER BY Rnd(-(1000*adID)*Time()))";

它显示正确的数据，但不是随机的，有什么建议吗？

我也提供了一个测试用样本，您可以从下面的链接下载 http://www.4shared.com/zip/qMSYRglGce/testorderby.html

Answer 1

在 UNION 查询中， ORDER BY 应该应用于 UNION 返回的整个集合因此，您可以从三个子选择中构建一组记录，然后将顺序应用于结果集。

string sql =  @"SELECT * FROM 
                (
                   SELECT TOP 100 PERCENT * FROM tbl_adv WHERE Stars = 7 
                     UNION 
                   SELECT TOP 84 PERCENT * FROM tbl_adv WHERE Stars = 6
                     UNION 
                   SELECT TOP 72 PERCENT * FROM tbl_adv WHERE Stars = 5
                )
                ORDER BY Rnd(-(1000*adID)*Time())";

订单不能使用union，microsoft access database，asp.net

1 个答案: