<p>How do I avoid read locks in my database?</p>

<p>Answers for multiple databases welcome!</p>

[{'answer_id': 37099, 'author': 'Joe Barone', 'author_id': 3452, 'author_profile': 'https://Stackoverflow.com/users/3452', 'pm_score': 2, 'selected': False, 'text': '<p>In SQL Server you can use the with(nolock) keyword in your select statements.  For example:</p>\n\n<pre><code>Select table1.columna, table2.columna\nfrom table1 with(nolock), table2 with(nolock)\n</code></pre>\n\n<p>Make sure to specify with(nolock) for each table/view in the query.</p>\n'}, {'answer_id': 37118, 'author': 'LucaM', 'author_id': 3511, 'author_profile': 'https://Stackoverflow.com/users/3511', 'pm_score': 3, 'selected': True, 'text': '<p>In Oracle the default mode of operation is the <em>Read committed</em> isolation level where a select statement is not blocked by another transaction modifying the data it\'s reading.\nFrom <a href="http://download.oracle.com/docs/cd/B10501_01/server.920/a96524/c21cnsis.htm" rel="nofollow noreferrer">Data Concurrency and Consistency</a>:</p>\n\n<blockquote>\n  <p>Each query executed by a transaction sees only data that was committed before the query (not the transaction) began. An Oracle query never reads dirty (uncommitted) data.</p>\n</blockquote>\n'}, {'answer_id': 37144, 'author': 'Douglas Tosi', 'author_id': 626, 'author_profile': 'https://Stackoverflow.com/users/626', 'pm_score': 2, 'selected': False, 'text': '<p>In Firebird writers never block readers and there are no dirty-reads. Only read-commited and snapshot isolation levels.<br>\nIt uses a multi-generational engine (like oracle i believe) instead of simple page or record locking.</p>\n'}, {'answer_id': 37436, 'author': 'Grey Panther', 'author_id': 1265, 'author_profile': 'https://Stackoverflow.com/users/1265', 'pm_score': 2, 'selected': False, 'text': '<p>PostgreSQL also uses MVCC (Multi-Version Concurrency Control), so using the default transaction isolation level (read-committed), you should never block, unless somebody is doing maintainace on th DB (dropping / adding columns / tables / indexes / etc).</p>\n'}]
['https://Stackoverflow.com/questions/37095', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/116/']