Question

鉴于我们在MS Access中有3个表，

表1

ID  MyName  Months
111 A         1
222 B         1
333 F         2
444 D         2
555 G         3
666 C         3

表2

ID  Income  Months
111 500       1
222 900       1
333 800       2
444 6000      2

表3

ID  Income  Months
555 65656   3
666 77777   3

我想将表2和表3加入到表1中，以便我的回归 Table_Result

ID  NAME    Income  Months
111 A       500        1
222 B       900        1
333 F       800        2
444 D      6000        2
555 G     65656        3
666 C     77777        3

如何获取Table_Result？

Answer 1

只需将UNION与LEFT JOIN一起使用时，您就不必使用Nz：

SELECT T1.ID,T1.MyName as Name, Nz(T2.Income,T3.Income) as Income,T1.Months
FROM Table1 T1 LEFT JOIN
     Table2 T2 ON T1.ID=T2.ID LEFT JOIN
     Table3 T3 ON T1.ID=T3.ID
ORDER BY T1.ID

<强>解释

如果第一个参数是Nz，则

null函数返回第二个参数。阅读更多here。

<强>结果：

ID  MyName  Income  Months
111 A       500     1
222 B       900     1
333 F       800     2
444 D       6000    2
555 G       65656   3
666 C       77777   3

mysql SQL fiddle中的示例结果（使用coalesce表示mysql而不是Nz）

Answer 2

尝试此查询

select  a.id,a.Myname,b.income,a.month
from table1 a
join table2 b on a.id=b.id
union all
select  a.id,a.Myname,c.income,a.month
from table1 a
join table3 c on c.id=a.id

Answer 3

您需要UNION table2和table3，然后将它们加入table1：

SELECT table1.*, table4.income FROM table1 LEFT JOIN 
  (SELECT * FROM table2 UNION SELECT * FROM table3) as table4 
  ON table4.Months = table1.Months AND table4.ID = table1.ID

您首先UNION table2和table3将其所有内容合并为一个“table4”，您只需在匹配的JOIN和{{1}上执行Months }。如果你真的不需要它，你最终可能想要删除ID的条件。

或者，您可以通过执行Months

来获得相同的结果

Answer 4

SELECT A.ID, A.MYNAME, A.MONTHS, B.INCOME
FROM Table1 AS A
INNER JOIN (SELECT * FROM Table2 UNION SELECT * FROM Table3) AS B ON B.ID = A.ID

Answer 5

您可以使用sql UNION运算符从2个或更多表中获取单个记录集

SELECT ID, Income, Months FROM table2
UNION
SELECT ID, Income, Months  FROM table3;

使用UNION解决您的问题的方法是：

Select t1.ID, t1.MyName, Table_Result.Income, t1.Months
  from Table1 t1
  join (SELECT ID, Income, Months FROM table2
        UNION
        SELECT ID, Income, Months  FROM table3) as Table_Result on Table_Result.id = t1.id;

如果您想要所有（重复的）值，您可以使用ALL运算符的UNION修饰符

Select t1.ID, t1.MyName, Table_Result.Income, t1.Months
  from Table1 t1
  join (SELECT ID, Income, Months FROM table2
        UNION ALL
        SELECT ID, Income, Months  FROM table3) as Table_Result on Table_Result.id = t1.id;

这是最后一个例子的sql fiddle

加入不同月份的多个表格

5 个答案: