Checks the database schema against one MySQL DDL query to see if it has been run.
Copyright: Copyright (C) 2005 - 2016 Open Source Matters, Inc. All rights reserved.
License: General Public License version 2 or later; see LICENSE
Located at Libraries/cms/schema/changeitem/mysql.php
Checks a DDL query to see if it is a known type If yes, build a check query to see if the DDL has been run on the database. If successful, the $msgElements, $queryType, $checkStatus and $checkQuery fields are populated. The $msgElements contains the text to create the user message. The $checkQuery contains the SQL query to check whether the schema change has been run against the current database. The $queryType contains the type of DDL query that was run (for example, CREATE_TABLE, ADD_COLUMN, CHANGE_COLUMN_TYPE, ADD_INDEX). The $checkStatus field is set to zero if the query is created