Returns information about server or database events. EVENTDATA is called when an event notification fires, and the results are returned to the specified service broker. EVENTDATA can also be used inside the body of a DDL or logon trigger.
EVENTDATA returns data only when referenced directly inside of a DDL or logon trigger. EVENTDATA returns null if it is called by other routines, even if those routines are called by a trigger.
Data returned by EVENTDATA is not valid after a transaction that called EVENTDATA, either implicitly or explicitly, commits or is rolled back.
EVENTDATA returns XML data. This data is sent to the client as Unicode that uses 2 bytes for each character. The following Unicode code points can be represented in the XML that is returned by EVENTDATA:
>= 0x0020 && <= 0xD7FF
>= 0xE000 && <= 0xFFFD Some characters that can appear in Transact-SQL identifiers and data are not expressible or permissible in XML. Characters or data that have code points not shown in the previous list are mapped to a question mark (?).
EVENTDATA returns a value of type xml. The schema returned for each event is comprised of elements nested inside an
<EVENT_INSTANCE> element. To obtain the schema returned for an event, use Index or Search to locate the topic for the event in SQL Server Books Online. The property names listed for the event correspond to elements returned in the schema, with the following exceptions:
- EVENTDATA returns a
<ServerName>element, instead of
- EVENTDATA returns an additional
For example, the ALTER_TABLE event returns the following schema:
<EVENT_INSTANCE> <EventType>type</EventType> <PostTime>date-time</PostTime> <SPID>spid</SPID> <ServerName>name</ServerName> <LoginName>name</LoginName> <UserName>name</UserName> <DatabaseName>name</DatabaseName> <SchemaName>name</SchemaName> <ObjectName>name</ObjectName> <ObjectType>type</ObjectType> <TSQLCommand>command</TSQLCommand> </EVENT_INSTANCE>
A. Querying event data in a DDL trigger
The following example creates a DDL trigger to prevent new tables from being created in the database. The Transact-SQL statement that fires the trigger is captured by using XQuery against the XML data that is generated by EVENTDATA. For more information, see XQuery Against the xml Data Type.
When you query the
<TSQLCommand> element by using Results to Grid in SQL Server Management Studio, line breaks in the command text do not appear. Use Results to Text instead.
USE AdventureWorks; GO CREATE TRIGGER safety ON DATABASE FOR CREATE_TABLE AS PRINT 'CREATE TABLE Issued.' SELECT EVENTDATA().value ('(/EVENT_INSTANCE/TSQLCommand/CommandText)','nvarchar(max)') RAISERROR ('New tables cannot be created in this database.', 16, 1) ROLLBACK ; GO --Test the trigger. CREATE TABLE NewTable (Column1 int); GO --Drop the trigger. DROP TRIGGER safety ON DATABASE GO
When you want to return event data, we recommend that you use the XQuery value() method instead of the query() method. The query() method returns XML and ampersand-escaped carriage return and line feed (CR/LF) instances in the output, while the value() method renders CR/LF instances invisible in the output.
B. Creating a log table with event data in a DDL trigger
The following example creates a table to store information about all database level events, and populates the table with a DDL trigger. The event type and Transact-SQL statement are captured by using XQuery against the XML data generated by EVENTDATA.
USE AdventureWorks; GO CREATE TABLE ddl_log (PostTime datetime, DB_User nvarchar(100), Event nvarchar(100), TSQL nvarchar(2000)); GO CREATE TRIGGER log ON DATABASE FOR DDL_DATABASE_LEVEL_EVENTS AS DECLARE @data XML SET @data = EVENTDATA() INSERT ddl_log (PostTime, DB_User, Event, TSQL) VALUES (GETDATE(), CONVERT(nvarchar(100), CURRENT_USER), @data.value('(/EVENT_INSTANCE/EventType)', 'nvarchar(100)'), @data.value('(/EVENT_INSTANCE/TSQLCommand)', 'nvarchar(2000)') ) ; GO --Test the trigger. CREATE TABLE TestTable (a int) DROP TABLE TestTable ; GO SELECT * FROM ddl_log ; GO --Drop the trigger. DROP TRIGGER log ON DATABASE GO --Drop table ddl_log. DROP TABLE ddl_log GO
Help and Information
12 December 2006