sql左匹选择条件

proc sql;

create table base_20_1 as select a.*,b.WEEK,b.n from base_20 as a

left join Weeklist as b on a.purchasedt>=b.START_2020 and a.purchasedt<=b.end_2020;

quit;

怎么将一个表匹配另一个可以满足选择条件的表：