SQL Server 2019

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create table table1
(
	id numeric,
	contractdatetime datetime,
	Attr3 varchar(100),
	Attr4 varchar(100),
	Attr5 varchar(100)
);
insert into table1 values (1, cast('2000-01-01 00:00:00.000' as datetime), 'a', 'a', 'a');
insert into table1 values (2, cast('2000-01-01 00:00:00.000' as datetime), 'b', 'b', 'b');
insert into table1 values (2, cast('2000-01-02 00:00:00.000' as datetime), null, null, null);
insert into table1 values (3, cast('2000-01-02 00:00:00.000' as datetime), 'SQL Server', 'SQL Server', 'SQL Server');
4 rows affected

select
	id,
	sum(
		convert(bigint, convert(varbinary, 
			substring(
				hashbytes('MD5',
					isnull(convert(varchar(19), contractdatetime, 20), 'null') +
					'-1-' + isnull(attr3, 'null') + '-2-' + isnull(attr3, 'null') + '-3-' + isnull(attr3, 'null'))
				, 1, 7)
			, 1))) hash
from table1
group by id
order by 1;


id
hash


1
50696302970576522

2
69171702324546493

3
7440319042693061