Snowflake snowsql merge statement for change tracking table - when not matched by target/source not allowed - merge

Question

I am trying to write a query logic to capture all changes from the source.
Merge should compare the keys in source and target and process the data accordingly. Below is an example, how can we achieve this in SQL server.
MERGE <target_table> [AS TARGET]
USING <table_source> [AS SOURCE]
ON <search_condition>
[WHEN MATCHED
THEN <merge_matched> ]
[WHEN NOT MATCHED [BY TARGET]
THEN <merge_not_matched> ]
[WHEN NOT MATCHED BY SOURCE
THEN <merge_matched> ];
In snowflake, I get below error while trying something similar,
Error SQL compilation error: syntax error line 7 at position 17 unexpected 'by'. syntax error line 8 at position 17 unexpected 'by'.
Is there a way in snowflake to handle 'when not matched by target' and 'when not matched by source' logic?
Thank you.

Answer 1

A workaround suggested by a teammate:
Define MATCHED_BY_SOURCE based on a full join, and look if a.col or b.col are null:
merge into TARGET t
using (
select <COLUMN_LIST>,
iff(a.COL is null, 'NOT_MATCHED_BY_SOURCE', 'MATCHED_BY_SOURCE') SOURCE_MATCH,
iff(b.COL is null, 'NOT_MATCHED_BY_TARGET', 'MATCHED_BY_TARGET') TARGET_MATCH
from SOURCE a
full join TARGET b
on a.COL = b.COL
) s
on s.COL = t.COL
when matched and s.SOURCE_MATCH = 'NOT_MATCHED_BY_SOURCE' then
<DO_SOMETHING>
when matched and s.TARGET_MATCH = 'NOT_MATCHED_BY_TARGET' then
<DO_SOMETHING_ELSE>
;