将两个 SELECT SQL MS Access 查询合并到一个查询中以制作一个包含两列的表

Question

对于 MS Access，我在 SQL 中有两个查询。 第一个是：

SELECT AVG(Salary) AS AverageSalary FROM Table WHERE EducationLevel = 1;

第二个查询：

SELECT AVG(Salary) AS AverageSalary2 FROM Table WHERE EducationLevel = 2;

如何将它们组合到一个查询中以生成包含两列的表，分别标记为“AverageSalary”和“AverageSalary2”？

Answer 1

可以一次查询完成。 考虑：

条件表达式：

SELECT Avg(IIf(EducationLevel = 1, Salary, Null)) AS AverageSalary, 
       Avg(IIf(EducationLevel = 2, Salary, Null)) AS AverageSalary2
FROM [Table];

或交叉表：

TRANSFORM Avg(Table.Salary) AS AvgOfSalary
SELECT 1 AS R
FROM [Table]
GROUP BY 1
PIVOT "AverageSalary" & [EducationLevel];

Answer 2

Below query, if the educational level field is a number field

 

     SELECT Avg(Switch([EducationalLevel]=1,[salary])) AS AverageSalary, 
     Avg(Switch([EducationalLevel]=2,[salary])) AS AverageSalary2
     FROM salary;

下面查询educationlevel字段是否为文本字段

   SELECT Avg(Switch([EducationalLevel]="1",[salary])) AS AverageSalary, 
    Avg(Switch([EducationalLevel]="2",[salary])) AS AverageSalary2
    FROM salary;