xudong963 commented on pull request #1339:
URL: https://github.com/apache/arrow-datafusion/pull/1339#issuecomment-974191228


   FYI, PostgreSQL has the following results.
   
   ```sql
   postgres=# create table table1 as SELECT * FROM (VALUES (1), (2), (null)) as 
t;
   SELECT 3
   postgres=# create table table2 as SELECT * FROM (VALUES (1), (3), (null)) as 
t;
   SELECT 3
   
   postgres=# SELECT *
   FROM table1
   LEFT JOIN table2
       ON table1.column1 = table2.column1
   WHERE table2.column1 IS NULL;
    column1 | column1
   ---------+---------
          2 |
            |
   (2 rows)
   
   postgres=# SELECT *
   FROM table1
   LEFT JOIN table2
       ON table1.column1 = table2.column1
   WHERE table2.column1 IS NOT NULL;
    column1 | column1
   ---------+---------
          1 |       1
   (1 row)
   
   postgres=# SELECT *
   FROM table2
   RIGHT JOIN table1
       ON table1.column1 = table2.column1
   WHERE table2.column1 IS NULL;
    column1 | column1
   ---------+---------
            |       2
            |
   (2 rows)
   
   postgres=# SELECT *
   FROM table2
   RIGHT JOIN table1
       ON table1.column1 = table2.column1
   WHERE table2.column1 IS NOT NULL;
    column1 | column1
   ---------+---------
          1 |       1
   (1 row)
   
   postgres=# SELECT *
   FROM table1
   FULL JOIN table2
       ON table1.column1 = table2.column1
   WHERE table2.column1 IS NULL;
    column1 | column1
   ---------+---------
          2 |
            |
            |
   (3 rows)
   
   postgres=# SELECT *
   FROM table1
   FULL JOIN table2
       ON table1.column1 = table2.column1
   WHERE table2.column1 IS NOT NULL;
    column1 | column1
   ---------+---------
          1 |       1
            |       3
   (2 rows)
   ```


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