总结一下:两种表达方式是等效的
方法一:
case
when tb1.os = 'android' then 'android'
when tb1.os = 'ios' then 'iPhone'
else 'PC'
end as os,
方法二:
case tb1.os
when 'android' then 'android'
when 'ios' then 'iPhone'
else 'PC'
end as os,
完整示例:
select user_id,
case location
when '北京' then '1'
else null
end as location_in_beijing
from employees
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