Hi Herman:
I guess what you mentioned before
```
if you are OK with slightly different NULL semantics then you could use NOT
EXISTS(subquery). The latter should perform a lot better.
```
is the NULL key1 of left table will be retained if NULL key2 is not found in
the right table ( join
Hi all:
From google , I know that:
Spark can only pick BroadcastNestedLoopJoin to implement left/right join.
but why I use following case , broascastnestedLoopJoin became Sortmerged
join when set spark.sql.autoBroadcastJoinThreshold=-1;
{code}
set spark
