Outer Joins

Joins that include all rows, regardless of whether there is a matching row, are called outer joins.

For example, the following query joins the titles and the titleauthor tables on their title_id column:
select * 
from titles, titleauthor
where titles.title_id *= titleauthor.title_id

SAP supports both Transact-SQL and ANSI outer joins. Transact-SQL outer joins use the *= command to indicate a left outer join and the =* command to indicate a right outer join. Transact-SQL outer joins were created by SAP as part of the Transact-SQL language.

ANSI outer joins use the keywords left join and right join to indicate a left and right join, respectively. SAP implemented the ANSI outer join syntax to fully comply with the ANSI standard. This is the previous example rewritten as an ANSI outer join:
select * 
from titles left join titleauthor
on titles.title_id = titleauthor.title_id
Related concepts
Transact-SQL Outer Joins
ANSI Inner and Outer Joins