*= in Sybase SQL

Question

I'm maintaining some code that uses a *= operator in a query to a Sybase database and I can't find documentation on it. Does anyone know what *= does? I assume that it is some sort of a join.

select * from a, b where a.id *= b.id

I can't figure out how this is different from:

select * from a, b where a.id = b.id

Answer 1

From http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.dc34982_1500/html/mig_gde/mig_gde160.htm:

Inner and outer tables

The terms outer table and inner table describe the placement of the tables in an outer join:

• In a left join, the outer table and inner table are the left and right tables respectively. The outer table and inner table are also referred to as the row-preserving and null-supplying tables, respectively.

• In a right join, the outer table and inner table are the right and left tables respectively.

For example, in the queries below, T1 is the outer table and T2 is the inner table:

• T1 left join T2
• T2 right join T1

Or, using Transact-SQL syntax:

• T1 *= T2
• T2 =* T1