Merge pull request #3745 from obacht17/patch-1

Describe null handling in anti join

docs/sql/query_syntax/from.md

@@ -273,7 +273,8 @@ USING (iata);
 Semi joins return rows from the left table that have at least one match in the right table.
 Anti joins return rows from the left table that have _no_ matches in the right table.
 When using a semi or anti join the result will never have more rows than the left hand side table.
-Semi and anti joins provide the same logic as [`IN`]({% link docs/sql/expressions/in.md %}) and `NOT IN` statements, respectively.
+Semi joins provide the same logic as [`IN`]({% link docs/sql/expressions/in.md %}) statements.
+Anti joins provide the same logic as `NOT IN` statements, except anti joins ignore `NULL` values from the right table.
 
 #### Semi Join Example
 
@@ -320,7 +321,7 @@ This query is equivalent with:
 ```sql
 SELECT *
 FROM city_airport
-WHERE iata NOT IN (SELECT iata FROM airport_names);
+WHERE iata NOT IN (SELECT iata FROM airport_names WHERE iata IS NOT NULL);
 ```
 
 ### Lateral Joins