case when then else end

查找住院,门诊的人数:

SELECT a.leixing,COUNT(a.leixing)
FROM
(SELECT
case resource_type
WHEN 'O' THEN '住院'
WHEN 'I' THEN '门诊'
ELSE '其他' END as leixing
FROM `doc_info_hive`) as a GROUP BY a.leixing;