这是我的第一篇文章，所以请温柔:)
我有几个疑问：
SELECT COUNT(DISTINCT(h.USERID))
FROM MHGROUP.USERHISTORY h with (NOLOCK)
JOIN MHGROUP.DOCUSERS u with (NOLOCK) on h.USERID = u.USERID
where h.CUSTOM2 = 'Work Web'
and h.ACTIONDATETIME >= GETUTCDATE()-30
and u.LOGIN = 'y'
SELECT COUNT(DISTINCT(h.USERID))
FROM MHGROUP.USERHISTORY h with (NOLOCK)
JOIN MHGROUP.DOCUSERS u with (NOLOCK) on h.USERID = u.USERID
where h.CUSTOM2 = 'Work Web'
and h.ACTIONDATETIME >= GETUTCDATE()-30
and u.LOGIN = 'y'
现在我被要求提取去年的数据，所以我想我会使用 case 语句，但无法弄清楚如何将不同的用户部分合并到 sum case 语句中......所以我得到了巨大的数字， 明显地
SELECT COUNT(DISTINCT(h.USERID))
FROM MHGROUP.USERHISTORY h with (NOLOCK)
JOIN MHGROUP.DOCUSERS u with (NOLOCK) on …