sql - CASE WHEN ELSE 何时改为 union？

Question

我想知道是否可以将 a 更改CASE when then else为 aunion all或类似的东西。

我希望这是可能的......

例子

CASE WHEN(C.Salutation = 'Dhr.' OR C.salutation = 'dhr.')
         THEN 'Meneer'+' '+ISNULL(C.middlename+' ','')+C.Lastname
    WHEN(C.Salutation = 'Mw.' OR C.salutation = 'mw.')
         THEN 'Mevrouw'+' '+ISNULL(C.middlename+' ','')+C.Lastname
    ELSE 'Meneer/Mevrouw '+ISNULL(C.middlename+' ','')+ISNULL(C.Lastname,'') END AS 'K5'

我希望你们能帮助我..

Answer 1

嗯，是的，你可以，但它很难看：

SELECT 'Meneer'+' '+ISNULL(C1.middlename+' ','')+C1.Lastname AS 'K5'
FROM table C1
WHERE C1.Salutation = 'Dhr.' OR C1.salutation = 'dhr.'
UNION
SELECT 'Mevrouw'+' '+ISNULL(C2.middlename+' ','')+C2.Lastname
FROM table C2
WHERE C2.Salutation = 'Mw.' OR C2.salutation = 'mw.'
UNION
SELECT 'Meneer/Mevrouw '+ISNULL(C.middlename+' ','')+ISNULL(C.Lastname,'')
FROM table C3
WHERE C3.Salutation != 'Mw.' AND C3.salutation != 'mw.'
AND C3.Salutation != 'Dhr.' AND C3.salutation != 'dhr.'