Question

我想加入两张桌子。

表A有一列，名为“Week”，包含52行：1,2,3,4,5,6等。表2有三列，名为“Name”，“Week”和“Total”，包含10行：

'Bob', 1, 1
'Bob', 3, 1
'Joe', 4, 1
'Bob', 6, 1

我想将这些加在一起，以便我的数据如下：

NAME|WEEK|TOTAL
'Bob', 1, 1
'Bob', 2, 0
'Bob', 3, 1
'Bob', 4, 0
'Bob', 5, 0
'Bob', 6, 1

如您所见，一个简单的外连接。但是，当我尝试这样做时，无论我使用什么样的连接，我都没有得到预期的结果。

我的查询如下：

SELECT a.WEEK, b.Total
FROM Weeks a LEFT JOIN Totals b ON (a.Week = b.Week and b.Name ='Bob')

此查询的结果是

NAME|WEEK|TOTAL
'Bob', 1, 1
'Bob', 3, 1
'Bob', 6, 1

提前感谢您的帮助！

Answer 1

我知道它的访问权限，但您的加入不正确。这里我们进入sql server..same概念，看看连接条件：

--dont worry about this code im just creating some temp tables

--table to store one column (mainly week number 1,2..52)
CREATE TABLE #Weeks
(
  weeknumber int
)

--insert some test data
--week numbers...I'll insert some for you
INSERT INTO #Weeks(weeknumber) VALUES(1)
INSERT INTO #Weeks(weeknumber) VALUES(2)
INSERT INTO #Weeks(weeknumber) VALUES(3)
INSERT INTO #Weeks(weeknumber) VALUES(4)
INSERT INTO #Weeks(weeknumber) VALUES(5)
INSERT INTO #Weeks(weeknumber) VALUES(6)

--create another table with two columns storing the week # and a total for that week
CREATE TABLE #Table2
 ( 
  weeknumber int,
  total int
 )

--insert some data
INSERT INTO #Table2(weeknumber, total) VALUES(1, 100)
--notice i skipped week 2 on purpose to show you the results
INSERT INTO #Table2(weeknumber, total) VALUES(3, 100)

--here's the magic
SELECT t1.weeknumber as weeknumber, ISNULL(t2.total,0) as total FROM 
#Weeks t1 LEFT JOIN #Table2 t2 ON t1.weeknumber=t2.weeknumber

--get rid of the temp tables
DROP TABLE #table2
DROP TABLE #Weeks

结果：

拿你的周数表（有一列的表：

SELECT t1.weeknumber as weeknumber

添加一个空检查以将空值替换为0.我认为访问中有一些内容，如ISNULL：

ISNULL(t2.total, 0) as total

从第一张桌子开始你的加入，然后离开加入你在daynumber字段的第二张桌子。结果很简单：

SELECT t1.weeknumber as weeknumber, ISNULL(t2.total,0) as total FROM 
#Weeks t1 LEFT JOIN #Table2 t2 ON t1.weeknumber=t2.weeknumber

不要注意我发布的所有其他代码，只是在那里创建临时表并在表格中插入值。

Answer 2

你是在正确的轨道上，但只需要使用左连接。如果total为空，则NZ函数将置0。

SELECT Totals.Person, Weeks.WeekNo, Nz(Totals.total, 0) as TotalAmount
FROM Weeks LEFT JOIN Totals 
ON (Weeks.WeekNo = Totals.weekno and Totals.Person = 'Bob');

编辑：您现在拥有的查询甚至不会给出您显示的结果，因为您遗漏了名称字段（这是一个字段的错误名称，因为它是一个保留字。）。你还没有提供所有的信息。此查询有效。

* 另一种方法：* 在Totals表上创建一个单独的查询，其中包含where子句：Name ='Bob'

Select Name, WeekNo, Total From Totals Where Name = 'Bob';

并将该查询替换为此查询中的Totals表。

Select b.Name, w.WeekNo, b.total
from Weeks as w 
LEFT JOIN qryJustBob as b
on .WeekNo = b.WeekNo;

Answer 3

SELECT b.Name, b.Week, b.Total
  FROM Totals AS b 
 WHERE b.Name ='Bob'
UNION
SELECT 'Bob' AS Name, a.Week, 0 AS Total
  FROM Weeks AS a 
 WHERE NOT EXISTS ( SELECT * 
                      FROM Totals AS b 
                     WHERE a.Week = b.Week
                           AND b.Name ='Bob' );

Access 97外部联接问题

3 个答案: