查询问题

Question

非常感谢，再次提前。

我所试图做的是列表中，如果一个机构n使用在医院H2 工程或具有 资格Q3或两者

我有两个表Agency_A &资格

Agency_A  
Nurse  Hospital 
Thomas  H1 
Taylor  H2 
Evans  H3 
Davies  H2 

Qualification 
Nurse  Qualification 
Thomas  Q2 
Taylor  Q3 
Evans  Q4 
Freeman Q3 

所以我'寻找

|TAYLOR |       {as she works in H2 and has qualification Q3} 
|FREEMAN |       {as she has qualification Q3} 
|DAVIES |       {as she works in H2 etc 

任何帮助，这将是伟大的。

Answer 1

这应该覆盖它：

SELECT 
    COALESCE(Qualification.Nurse, Agency_A.Nurse) 
FROM (
    SELECT DISTINCT Nurse 
    FROM Agency_A 
    WHERE Hospital = 'H2') Agency_A 
LEFT OUTER JOIN (
    SELECT DISTINCT Nurse 
    FROM Qualification 
    WHERE Qualification = 'Q3') Qualification 
ON Agency_A.Nurse = Qualification.Nurse 

这覆盖的情况下护士是在一个表而不是其他。