請告訴如何if語句CASE條件在mysql中使用2005年

Question

Table :-Person 
Column:-day_phone, alt_phone ,Home_phone 

條件： - 如果day_phone爲null，則alt_phone
如果兩個沒有數據那麼複製HOME_PHONE

Answer 1

的應用情況，並與運營商

select Person 
    , case when day_phone is null then alt_phone 
     when day_phone is null and lt_phone is null then Home_phone 
    end 
    from my_table 

Answer 2

你可以使用COALESCE函數將返回第一個非空值：

select coalesce(day_phone, alt_phone, Home_phone) 
from person