【发布时间】：2018-02-21 13:11:20
【问题描述】：
我正在尝试从 3 个不同组/存储桶的 Access 表中收集随机记录样本。在我的示例中，我希望每个 [Duration of the Call] 存储桶中有 50 条随机记录，总共 150 条记录。我用一个 UNION 子句加入每个组。返回的结果不是随机的，每个 50 个存储桶只是从 2018 年 1 月 2 日的第一个调用日期中提取的。就像 TOP 子句只是查看表中与条件匹配的前 50 条记录，但我想要从整个表中真正随机抽样。谢谢
SELECT * FROM (
SELECT TOP 50
[Workgroup],[Last Name],[First Name],[Titanium Number],
[Phone Number], [Inbound-Outbound], [Date of the Call], [Time of the Call],
[Duration of the Call], ID
FROM PCA_Calls WHERE
([Date of the Call] >= #1/1/2018# ) AND
([Date of the Call] <= #1/31/2018# ) AND
([Duration of the Call] >= 420) AND ([Duration of the Call] <=900) AND
([Workgroup] = "PCA0001A" )
UNION
SELECT TOP 50
[Workgroup],[Last Name],[First Name],[Titanium Number],
[Phone Number], [Inbound-Outbound], [Date of the Call], [Time of the Call],
[Duration of the Call], ID
FROM PCA_Calls WHERE
([Date of the Call] >= #1/1/2018# ) AND
([Date of the Call] <= #1/31/2018# ) AND
([Duration of the Call] >= 901) AND ([Duration of the Call] <=1800) AND
([Workgroup] = "PCA0001A" )
UNION
SELECT TOP 50
[Workgroup],[Last Name],[First Name],[Titanium Number],
[Phone Number], [Inbound-Outbound], [Date of the Call], [Time of the Call],
[Duration of the Call], ID
FROM PCA_Calls WHERE
([Date of the Call] >= #1/1/2018# ) AND
([Date of the Call] <= #1/31/2018# ) AND
([Duration of the Call] >= 1801) AND ([Duration of the Call] <=2700) AND
([Workgroup] = "PCA0001A" )
) AS Sub ORDER BY rnd(INT(NOW*ID)-NOW*ID);enter code here
【问题讨论】：
-
将顺序移动到联合中的每个查询
-
这些建议都不起作用
-
如果某些东西不起作用，请说明您是如何应用它的，以及您的意思是什么不起作用。您是否收到错误、意外结果等
-
将 ORDER BY 添加到 UNION 中的每个查询都会产生错误“ORDER BY 表达式 (Rnd(-1000*ID)*Time())) 包含查询未选择的字段. 只有在第一个查询中请求的那些字段才能包含在 ORDER BY 表达式中”。使用 UNION 时只能有 1 个 ORDER BY。
-
只需使用子查询来避免该错误。 (
SELECT * FROM (SELECT TOP 50 etc FROM something ORDER BY something))