问题来自
joins中的不等式条件。这带来了问题。以下内容可能足以满足您的目的：
create table tmp_leads2 as select t1.*,(case when s1.period is not null then 'Y' else 'N' end) as flag_cur,(case when s2.period is not null then 'Y' else 'N' end) as flag_prev,s1.cutoff_date as cutoff_date_cur, s1.cutoff_dtkey as cutoff_dtkey_cur ,s2.cutoff_date as cutoff_date_prev, s2.cutoff_dtkey as cutoff_dtkey_prev from tmp_leads t1 left join param s1 on s1.period = '(a) Current' left joinparam s2 on s2.period = '(b) Previous' where (s1.begin_date is null or s1.begin_date <= t1.CreatedDate and t1.CreatedDate < s1.end_date) or (s2.begin_date is null or s2.begin_date <= t1.CreatedDate and t1.CreatedDate < s2.end_date);
这并不完全等效。它假设如果表中有参数，则所有日期都在表中。那可能是一个合理的假设。如果不是，则将需要更复杂的查询。
