我有两个要加入的表。
表 A 有一列，名为“周”，包含 52 行：1、2、3、4、5、6 等。表 2 有三列，名为“名称”、“周”和“总”，并且包含 10 行：
'Bob', 1, 1
'Bob', 3, 1
'Joe', 4, 1
'Bob', 6, 1
我想将这些连接在一起，以便我的数据看起来像：
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，无论我使用哪种联接，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')
这个查询的结果是
NAME|WEEK|TOTAL
'Bob', 1, 1
'Bob', 3, 1
'Bob', 6, 1
在此先感谢您的帮助！
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.. 相同的概念只看连接条件：
--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：
1 100
2 0
3 100
4 0
5 0
6 0
拿你的周数表（只有一列的表：
SELECT t1.weeknumber as weeknumber
添加一个空检查以用 0 替换空值。我认为访问中有一些内容，例如ISNULL：
ISNULL(t2.total, 0) as total
并从您的第一个表开始您的连接，并在 weeknumber 字段上左连接到您的第二个表。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，它们只是用于创建临时表并将值插入表中。
你在正确的轨道上，但只需要使用左连接。如果 total 为空，则 NZ 函数也会输入 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：您现在的查询甚至不会给出您显示的结果，因为您遗漏了 Name 字段（这对于字段来说是一个错误的名称，因为它是一个保留字。）。您仍然没有提供所有信息。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';
并将该查询替换为该查询中的 Totals 表。
Select b.Name, w.WeekNo, b.total
from Weeks as w
LEFT JOIN qryJustBob as b
on .WeekNo = b.WeekNo;
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' );