<p>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.</p>

<pre><code>select * from a, b where a.id *= b.id</code></pre>

<p>I can't figure out how this is different from:</p>

<pre><code>select * from a, b where a.id = b.id</code></pre>

[{'answer_id': 40671, 'author': 'Lasse V. Karlsen', 'author_id': 267, 'author_profile': 'https://Stackoverflow.com/users/267', 'pm_score': 3, 'selected': False, 'text': "<p>It means outer join, a simple = means inner join.</p>\n\n<pre><code>*= is LEFT JOIN and =* is RIGHT JOIN.\n</code></pre>\n\n<p>(or vice versa, I keep forgetting since I'm not using it any more, and Google isn't helpful when searching for *=)</p>\n"}, {'answer_id': 40684, 'author': 'Adam Tegen', 'author_id': 4066, 'author_profile': 'https://Stackoverflow.com/users/4066', 'pm_score': 5, 'selected': True, 'text': '<p>From <a href="http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.dc34982_1500/html/mig_gde/mig_gde160.htm" rel="noreferrer">http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.dc34982_1500/html/mig_gde/mig_gde160.htm</a>:</p>\n\n<p>Inner and outer tables</p>\n\n<p>The terms outer table and inner table describe the placement of the tables in an outer join:</p>\n\n<ul>\n<li><p>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.</p></li>\n<li><p>In a right join, the outer table and inner table are the right and left tables respectively.</p></li>\n</ul>\n\n<p>For example, in the queries below, T1 is the outer table and T2 is the inner table:</p>\n\n<ul>\n<li>T1 left join T2</li>\n<li>T2 right join T1</li>\n</ul>\n\n<p>Or, using Transact-SQL syntax:</p>\n\n<ul>\n<li>T1 *= T2</li>\n<li>T2 =* T1</li>\n</ul>\n'}, {'answer_id': 40698, 'author': 'Joel Coehoorn', 'author_id': 3043, 'author_profile': 'https://Stackoverflow.com/users/3043', 'pm_score': 3, 'selected': False, 'text': '<p>Of course, you <em>should</em> write it this way:</p>\n\n<pre><code>SELECT *\nFROM a\nLEFT JOIN b ON b.id=a.id\n</code></pre>\n\n<p>The a,b syntax is evil.</p>\n'}, {'answer_id': 40700, 'author': 'Adam Tegen', 'author_id': 4066, 'author_profile': 'https://Stackoverflow.com/users/4066', 'pm_score': 1, 'selected': False, 'text': "<pre><code>select * from a, b where a.id = b.id</code></pre>\n\n<p>Requires that a row exist in where b.id = a.id in order to return an answer</p>\n\n<pre><code>select * from a, b where a.id *= b.id</code></pre>\n\n<p>Will fill the columns from b with nulls when there wasn't a row in b where b.id = a.id.</p>\n"}, {'answer_id': 40702, 'author': 'jason saldo', 'author_id': 1293, 'author_profile': 'https://Stackoverflow.com/users/1293', 'pm_score': 3, 'selected': False, 'text': '<p>ANSI-82 syntax  </p>\n\n<pre><code>select \n    * \nfrom \n    a\n  , b \n\nwhere \n     a.id *= b.id\n</code></pre>\n\n<p>ANSI-92</p>\n\n<pre><code>select \n    * \nfrom \n   a\n  left outer join b \n      on a.id = b.id\n</code></pre>\n'}]
['https://Stackoverflow.com/questions/40665', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/4066/']