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create table a (subjectid int, groupid int, _groupid int); create table b (groupid int, subjectid int); insert into a select 5,null,1; insert into a select 5,null,2; insert into a select 6,null,1; insert into b select 18,5; insert into b select 19,5; insert into b select 25,6;
 hidden batch(es)


update a join ( select *, row_number() over(partition by subjectid order by groupid) _groupid from b )b on a.subjectid=b.subjectid and a._groupid=b._groupid set a.groupid=b.groupid
 hidden batch(es)


select * from a
subjectid groupid _groupid
5 18 1
5 19 2
6 25 1
 hidden batch(es)