Question

这是我的问题。我正在创建4个临时表来计算特定类型的盒子和员工的工作时间。给定开始日期和结束日期，我们想知道每种类型（1,2和3）的总箱数以及它们在该时间段内的总工作时数。如果每种类型中至少有一种类型，则所有方法都可以正常工作，但如果只存在两种类型，那么我将得到整个最终SELECT语句的空白结果。

那么，在FROM行中包含空临时表的SELECT语句是否会导致其他所有内容返回空白？

例如，日期范围6-1-10到6-10-10返回10个类型1框，12个类型2框，0个类型3框和36小时，但显示的结果为空白。但如果它延长了一天，并且包含了15个类型3的框，则查询可以正常工作。

SELECT Count(isnull(Box_Num,0)) as Box1, emp_num INTO #Box1
FROM  TEST.dbo.Prod_beta2
WHERE BoxType like '1' and time  > '06/01/10' + ' 12:01 AM'  and time  < '06/10/10' + ' 11:59pm' and emp_num like '10467'
group by emp_num


SELECT Count(isnull(Box_Num,0)) as Box2, emp_num INTO #Box2
FROM TEST.dbo.Prod_beta2
WHERE BoxType like '2' and time > '06/01/10' + ' 12:01 AM' and time < '06/10/10' + ' 11:59pm' and emp_num like '10467'
group by emp_num


SELECT count(isnull(box_num,0)) as Box3, emp_num INTO #Box3
from TEST.dbo.Prod_beta2
WHERE BoxType like '3' and time > '06/01/10' + '  12:01 AM' and time < '06/10/10' + ' 11:59pm' and emp_num like '10467'
group by emp_num


SELECT SUM(HOURS) as TotalHours, empid INTO #Hours
FROM TEST.dbo.Timeclock
where timein > '06/01/10' + ' 12:01 AM' and timein < '06/10/10' + ' 11:59pm' and empid like '10467'
group by empid


SELECT Box1, Box2, Box3, TotalHours
FROM #Box1, #Box2, #Box3, #Hours


DROP TABLE #Box1, #Box2, #Box3, #Hours

Answer 1

是。您正在做笛卡尔积，这意味着您将在结果中包含B1 * B2 * B3 * H行。

当B3没有行时，你显然会乘以零。

前三个条件可以轻松组合（顺便说一下BoxType和emp_num的数据类型是什么？如果它们是数字，那么不要使用字符串来避免任何不必要的类型转换问题。此外，您的日期逻辑似乎在11:59 pm到12:01 AM之间遗漏了任何内容。这是故意吗？此外，如果您更换服务器等，您应该使用ISO日期格式以避免任何问题。）

SELECT 
Count(CASE WHEN BoxType = '1' THEN 1 ELSE NULL END) as Box1,
 Count(CASE WHEN BoxType = '2' THEN 1 ELSE NULL END) as Box2,
 Count(CASE WHEN BoxType = '3' THEN 1 ELSE NULL END) as Box3
FROM  TEST.dbo.Prod_beta2
WHERE BoxType in ('1','2','3') and time  > '06/01/10' + ' 12:01 AM'  and 
  time  < '06/10/10' + ' 11:59pm' and emp_num like '10467'
group by emp_num

Answer 2

如果字段都是相同的类型，那么你不应该这样做：

SELECT Box1, Box2, Box3, TotalHours 
FROM #Box1, #Box2, #Box3, #Hours

您应该使用UNION ALL查询

像这样：

   SELECT Count(isnull(Box_Num,0)) as Box1, emp_num
    FROM  TEST.dbo.Prod_beta2 
    WHERE BoxType like '1' and time  > '06/01/10' + ' 12:01 AM'  and time  < '06/10/10' + ' 11:59pm' and emp_num like '10467' 
    UNION ALL
    SELECT Count(isnull(Box_Num,0)) as Box2, emp_num
    FROM TEST.dbo.Prod_beta2 
    WHERE BoxType like '2' and time > '06/01/10' + ' 12:01 AM' and time < '06/10/10' + ' 11:59pm' and emp_num like '10467' 
    UNION ALL

SELECT count(isnull(box_num,0)) as Box3, emp_num
from TEST.dbo.Prod_beta2
WHERE BoxType like '3' and time > '06/01/10' + '  12:01 AM' and time < '06/10/10' + ' 11:59pm' and emp_num like '10467'
group by emp_num

您的上一次选择是唯一不同的，所以只是将查询与显示的框数分开。

但是，你甚至不需要临时表，只需使用标准的SELECT语句，并为每个语句添加union all。

如果其中任何一个查询包含0行，则当前语句将产生0行。 Look into cartesian products and what they mean

可以从SQL中的一个空临时表中选择导致结果为空吗？

2 个答案: