Creating audit triggers in SQL Server
I need to implement change tracking on two tables in my SQL Server 2005 database. I need to audit additions, deletions, updates (with detail on what was updated). I was planning on using a trigger to do this, but it seams that this is easy to do this incorrectly.
Can anybody post an example of an update trigger that accomplishes this successfully and in an elegant manner? I am hoping to end up with an audit table开发者_C百科 with the following structure:
- ID
- LogDate
- TableName
- TransactionType (update/insert/delete)
- RecordID
- FieldName
- OldValue
- NewValue
... thoughts?
I just want to call out couple of points:
Use code generators You can't have a single procedure to track all tables, you will need to generate similar but distinct triggers on each tracked table. This kind of job is best suited for automated code generation. In your place I would use an XSLT transformation to generate the code from XML, and the XML can be generated automatically from metadata. This allows you to easily maintain the triggers by regenerating them each time you make a change to the audit logic/structure or a target table is added/altered.
Consider capacity planning for the audit. An audit table that tracks all value changes will be, by far, the biggest table in the database: it will contain all the current data and all the history of the current data. Such a table will increase the database size by 2-3 orders of magnitude (x10, x100). And the audit table will quickly become the bottleneck of everything:
- every DML operation will require locks in the audit table
- all administrative and maintenance operations will have to accommodate the size of the database due to audit
Take into account the schema changes. A table named 'Foo' may be dropped and later a different table named 'Foo' may be created. The audit trail has to be able to distinguish the two different objects. Better use a slow changing dimension approach.
Consider the need to efficiently delete audit records. When the retention period dictated by your application subject policies is due, you need to be able to delete the due audit records. It may not seem such a big deal now, but 5 years later when the first records are due the audit table has grown to 9.5TB it may be a problem.
Consider the need to query the audit. The audit table structure has to be prepared to respond efficiently to the queries on audit. If your audit cannot be queried then it has no value. The queries will be entirely driven by your requirements and only you know those, but most audit records are queried for time intervals ('what changes occurred between 7pm and 8pm yesterday?'), by object ('what changes occurred to this record in this table?') or by author ('what changes did Bob in the database?').
We are using ApexSQL Audit that generates audit triggers and below are data structures used by this tool. If you don’t plan on buying a 3rd party solution you can install this tool in trial mode, see how they implemented triggers and storage and then create something similar for yourself.
I didn’t bother getting into too many details on how these tables work but hopefully this will get you started.
There is no generic way to do it the way you want. Ultimately you end up writing reams of code for each table. Not to mention it can be fairy slow if you need to compare each column for change.
Also the fact that you might be updating multiple rows at the same time implies you need to open a cursor to loop through all the records.
The way I'd do it will be using table with structure identical to the tables you are tracking and unpivot it later to show which columns have actually changed. I'd also keep track of the session that actually did the change. This assumes that you have primary key in the table being tracked.
So given a table like this
CREATE TABLE TestTable
(ID INT NOT NULL CONSTRAINT PK_TEST_TABLE PRIMARY KEY,
Name1 NVARCHAR(40) NOT NULL,
Name2 NVARCHAR(40))
I'd create an audit table like this in the audit schmea.
CREATE TABLE Audit.TestTable
(SessionID UNIQUEIDENTIFER NOT NULL,
ID INT NOT NULL,
Name1 NVARCHAR(40) NOT NULL,
Name2 NVARCHAR(40),
Action NVARCHAR(10) NOT NULL CONSTRAINT CK_ACTION CHECK(Action In 'Deleted','Updated'),
RowType NVARCHAR(10) NOT NULL CONSTRAINT CK_ROWTYPE CHECK (RowType in 'New','Old','Deleted'),
ChangedDate DATETIME NOT NULL Default GETDATE(),
ChangedBy SYSNHAME NOT NULL DEFAULT USER_NAME())
And a trigger for Update like this
CREATE Trigger UpdateTestTable ON DBO.TestTable FOR UPDATE AS
BEGIN
SET NOCOUNT ON
DECLARE @SessionID UNIQUEIDENTIFER
SET @SessionID = NEWID()
INSERT Audit.TestTable(Id,Name1,Name2,Action,RowType,SessionID)
SELECT ID,name1,Name2,'Updated','Old',@SessionID FROM Deleted
INSERT Audit.TestTable(Id,Name1,Name2,Action,RowType,SessionID)
SELECT ID,name1,Name2,'Updated','New',@SessionID FROM Inserted
END
This runs quite fast. During reporting , you simply join the rows based on sessionID, and Primary key and produce a report. Alternatively you can have a batch job that periodically goes through all the tables in the audit table and prepare a name-value pair showing the changes.
HTH
It looks simple and should work well until you have image/varbinary etc elements in your tables You have whole old record and whole new record as xml. Should also work properly for inserting multiple columns at 1 batch.
CREATE TABLE _AuditTable
(Aud_Id int identity(1,1) primary key,
Aud_TableName varchar(100),
Aud_ActionType char(1),
Aud_Username varchar(100),
Aud_OLDValues xml,
Aud_NEWValues xml,
Aud_OperationDate datetime DEFAULT GETDATE()
)
And trigger code
CREATE TRIGGER _test2_InsertUpdate on _test2
FOR INSERT, UPDATE
AS
BEGIN
SET NOCOUNT ON;
IF NOT EXISTS(SELECT 1 FROM deleted) AND NOT EXISTS(SELECT 1 FROM inserted)
RETURN;
declare @tablename varchar(100)
SELECT @tablename = OBJECT_NAME(parent_object_id)
FROM sys.objects
WHERE sys.objects.name = OBJECT_NAME(@@PROCID)
/*Action*/
DECLARE @ActionType char(1)
IF EXISTS (SELECT * FROM inserted)
IF EXISTS (SELECT * FROM deleted)
SELECT @ActionType = 'U'
ELSE
SELECT @ActionType = 'I'
ELSE
SELECT @ActionType = 'D'
declare @inserted xml, @deleted xml
SET @inserted = (SELECT * FROM inserted FOR XML PATH)
SET @deleted = (SELECT * FROM deleted FOR XML PATH)
INSERT INTO _AuditTable(Aud_TableName, Aud_ActionType, Aud_Username, Aud_OLDValues, Aud_NEWValues)
SELECT @tablename, @ActionType, SUSER_SNAME(), @deleted, @inserted
END
OUTPUT
Aud_Id | Aud_TableName | Aud_ActionType | Aud_Username | Aud_OLDValues | Aud_NEWValues | Aud_OperationDate
1 |_test2 | I |abc\mR | NULL |<row><name>abc</name></row> | 2018-11-07 12:38:34.937
I finally found a universal solution, that does not require dynamic sql and logs changes of all columns.
Its not needed to change the trigger if the table changes.
This is the audit log:
CREATE TABLE [dbo].[Audit](
[ID] [bigint] IDENTITY(1,1) NOT NULL,
[Type] [char](1) COLLATE Latin1_General_CI_AS NULL,
[TableName] [nvarchar](128) COLLATE Latin1_General_CI_AS NULL,
[PK] [int] NULL,
[FieldName] [nvarchar](128) COLLATE Latin1_General_CI_AS NULL,
[OldValue] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL,
[NewValue] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL,
[UpdateDate] [datetime] NULL,
[Username] [nvarchar](8) COLLATE Latin1_General_CI_AS NULL,
CONSTRAINT [PK_AuditB] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
This is the trigger for one table:
INSERT INTO ILSe.dbo.Audit ([Type], TableName, PK, FieldName, OldValue, NewValue, Username)
SELECT
CASE WHEN NOT EXISTS (SELECT ID FROM deleted WHERE ID = ISNULL(ins.PK,del.PK)) THEN 'I'
WHEN NOT EXISTS (SELECT ID FROM inserted WHERE ID = ISNULL(ins.PK,del.PK)) THEN 'D'
ELSE 'U' END as [Type],
'AGB' as TableName,
ISNULL(ins.PK,del.PK) as PK,
ISNULL(ins.FieldName,del.FieldName) as FieldName,
del.FieldValue as OldValue,
ins.FieldValue as NewValue,
ISNULL(ins.Username,del.Username) as Username
FROM (SELECT
insRowTbl.PK,
insRowTbl.Username,
attr.insRow.value('local-name(.)', 'nvarchar(128)') as FieldName,
attr.insRow.value('.', 'nvarchar(max)') as FieldValue
FROM (Select
i.ID as PK,
i.LastModifiedBy as Username,
convert(xml, (select i.* for xml raw)) as insRowCol
from inserted as i
) as insRowTbl
CROSS APPLY insRowTbl.insRowCol.nodes('/row/@*') as attr(insRow)
) as ins
FULL OUTER JOIN (SELECT
delRowTbl.PK,
delRowTbl.Username,
attr.delRow.value('local-name(.)', 'nvarchar(128)') as FieldName,
attr.delRow.value('.', 'nvarchar(max)') as FieldValue
FROM (Select
d.ID as PK,
d.LastModifiedBy as Username,
convert(xml, (select d.* for xml raw)) as delRowCol
from deleted as d
) as delRowTbl
CROSS APPLY delRowTbl.delRowCol.nodes('/row/@*') as attr(delRow)
) as del
on ins.PK = del.PK and ins.FieldName = del.FieldName
WHERE
isnull(ins.FieldName,del.FieldName) not in ('LastModifiedBy', 'ID', 'TimeStamp')
and ((ins.FieldValue is null and del.FieldValue is not null)
or (ins.FieldValue is not null and del.FieldValue is null)
or (ins.FieldValue != del.FieldValue))
This trigger is for one Table named AGB. The Table with the name AGB has a primary Key Column with the name ID and a Column with the Name LastModifiedBy which contains the username that made the last edit.
The trigger consists of two parts, first it converts columns of inserted and deleted tables into rows. This is explained in detail here: https://stackoverflow.com/a/43799776/4160788
Then it joins the rows (one row per column) of the inserted and deleted tables by primary key and field name, and logs a line for each changed column. It does NOT log changes of ID, TimeStamp or LastModifiedByColumn.
You can insert your own TableName, Columns names.
You can also create the following stored procedure, and then call this stored procedure to generate your triggers:
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[_create_audit_trigger]') AND type in (N'P', N'PC'))
BEGIN
EXEC dbo.sp_executesql @statement = N'CREATE PROCEDURE [dbo].[_create_audit_trigger] AS'
END
ALTER PROCEDURE [dbo].[_create_audit_trigger]
@TableName varchar(max),
@IDColumnName varchar(max) = 'ID',
@LastModifiedByColumnName varchar(max) = 'LastModifiedBy',
@TimeStampColumnName varchar(max) = 'TimeStamp'
AS
BEGIN
PRINT 'start ' + @TableName + ' (' + @IDColumnName + ', ' + @LastModifiedByColumnName + ', ' + @TimeStampColumnName + ')'
/* if you have other audit trigger on this table and want to disable all triggers, enable this:
EXEC ('ALTER TABLE ' + @TableName + ' DISABLE TRIGGER ALL')*/
IF EXISTS (SELECT * FROM sys.objects WHERE [type] = 'TR' AND [name] = 'tr_audit_'+@TableName)
EXEC ('DROP TRIGGER [dbo].tr_audit_'+@TableName)
EXEC ('
CREATE TRIGGER [dbo].[tr_audit_'+@TableName+'] ON [ILSe].[dbo].['+@TableName+'] FOR INSERT, UPDATE, DELETE
AS
BEGIN
SET NOCOUNT ON;
INSERT INTO ILSe.dbo.Audit ([Type], TableName, PK, FieldName, OldValue, NewValue, Username)
SELECT CASE WHEN NOT EXISTS (SELECT '+@IDColumnName+' FROM deleted WHERE '+@IDColumnName+' = ISNULL(ins.PK,del.PK)) THEN ''I'' WHEN NOT EXISTS (SELECT '+@IDColumnName+' FROM inserted WHERE '+@IDColumnName+' = ISNULL(ins.PK,del.PK)) THEN ''D'' ELSE ''U'' END as [Type],
'''+@TableName+''' as TableName, ISNULL(ins.PK,del.PK) as PK, ISNULL(ins.FieldName,del.FieldName) as FieldName, del.FieldValue as OldValue, ins.FieldValue as NewValue, ISNULL(ins.Username,del.Username) as Username FROM
(SELECT insRowTbl.PK, insRowTbl.Username, attr.insRow.value(''local-name(.)'', ''nvarchar(128)'') as FieldName, attr.insRow.value(''.'', ''nvarchar(max)'') as FieldValue FROM (Select
i.'+@IDColumnName+' as PK,
i.'+@LastModifiedByColumnName+' as Username,
convert(xml, (select i.* for xml raw)) as insRowCol
from inserted as i) as insRowTbl
CROSS APPLY insRowTbl.insRowCol.nodes(''/row/@*'') as attr(insRow)) as ins
FULL OUTER JOIN
(SELECT delRowTbl.PK, delRowTbl.Username, attr.delRow.value(''local-name(.)'', ''nvarchar(128)'') as FieldName, attr.delRow.value(''.'', ''nvarchar(max)'') as FieldValue FROM (Select
d.'+@IDColumnName+' as PK,
d.'+@LastModifiedByColumnName+' as Username,
convert(xml, (select d.* for xml raw)) as delRowCol
from deleted as d) as delRowTbl
CROSS APPLY delRowTbl.delRowCol.nodes(''/row/@*'') as attr(delRow)) as del on ins.PK = del.PK and ins.FieldName = del.FieldName
WHERE isnull(ins.FieldName,del.FieldName) not in ('''+@LastModifiedByColumnName+''', '''+@IDColumnName+''', '''+@TimeStampColumnName+''') and
((ins.FieldValue is null and del.FieldValue is not null) or (ins.FieldValue is not null and del.FieldValue is null) or (ins.FieldValue != del.FieldValue))
END
')
PRINT 'end ' + @TableName
PRINT ''
END
Each table one wants to monitor, will need its own trigger. It is pretty obvious, that - as pointed out in the accepted answer - code generation will be a good thing.
If you like this approach, it might be an idea to use this trigger and replace some generic steps with generated code for each table separately.
Nevertheless I created a fully generic Audit-Trigger. The observed table must have a PK, but this PK might even be multi-column.
Some column types (like BLOBs) might not work, but you could easily exclude them.
This will not be the best in performance :-D
To be honest: This is more kind of an exercise...
SET NOCOUNT ON;
GO
CREATE TABLE AuditTest(ID UNIQUEIDENTIFIER
,LogDate DATETIME
,TableSchema VARCHAR(250)
,TableName VARCHAR(250)
,AuditType VARCHAR(250),Content XML);
GO
--Some table to test this (used quirky PK columns on purpose...)
CREATE TABLE dbo.Testx(ID1 DATETIME NOT NULL
,ID2 UNIQUEIDENTIFIER NOT NULL
,Test1 VARCHAR(100)
,Test2 DATETIME);
--Add a two column PK
ALTER TABLE dbo.Testx ADD CONSTRAINT PK_Test PRIMARY KEY(ID1,ID2);
--Some test data
INSERT INTO dbo.Testx(ID1,ID2,Test1,Test2) VALUES
({d'2000-01-01'},NEWID(),'Test1',NULL)
,({d'2000-02-01'},NEWID(),'Test2',{d'2002-02-02'});
--This is the current content
SELECT * FROM dbo.Testx;
GO
--The trigger for the audit
CREATE TRIGGER [dbo].[UpdateTestTrigger]
ON [dbo].[Testx]
FOR UPDATE,INSERT,DELETE
AS
BEGIN
IF NOT EXISTS(SELECT 1 FROM deleted) AND NOT EXISTS(SELECT 1 FROM inserted) RETURN;
SET NOCOUNT ON;
DECLARE @tableSchema VARCHAR(250);
DECLARE @tableName VARCHAR(250);
DECLARE @AuditID UNIQUEIDENTIFIER=NEWID();
DECLARE @LogDate DATETIME=GETDATE();
SELECT @tableSchema = sch.name
,@tableName = tb.name
FROM sys.triggers AS tr
INNER JOIN sys.tables AS tb ON tr.parent_id=tb.object_id
INNER JOIN sys.schemas AS sch ON tb.schema_id=sch.schema_id
WHERE tr.object_id = @@PROCID
DECLARE @tp VARCHAR(10)=CASE WHEN EXISTS(SELECT 1 FROM deleted) AND EXISTS(SELECT 1 FROM inserted) THEN 'upd'
ELSE CASE WHEN EXISTS(SELECT 1 FROM deleted) AND NOT EXISTS(SELECT 1 FROM inserted) THEN 'del' ELSE 'ins' END END;
SELECT * INTO #tmpInserted FROM inserted;
SELECT * INTO #tmpDeleted FROM deleted;
SELECT kc.ORDINAL_POSITION, kc.COLUMN_NAME
INTO #tmpPKColumns
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS tc
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS kc ON tc.TABLE_CATALOG=kc.TABLE_CATALOG
AND tc.TABLE_SCHEMA=kc.TABLE_SCHEMA
AND tc.TABLE_NAME=kc.TABLE_NAME
AND tc.CONSTRAINT_NAME=kc.CONSTRAINT_NAME
AND tc.CONSTRAINT_TYPE='PRIMARY KEY'
WHERE tc.TABLE_SCHEMA=@tableSchema
AND tc.TABLE_NAME=@tableName
ORDER BY kc.ORDINAL_POSITION;
DECLARE @pkCols VARCHAR(MAX)=
STUFF
(
(
SELECT 'UNION ALL SELECT ''' + pc.COLUMN_NAME + ''' AS [@name] , CAST(COALESCE(i.' + QUOTENAME(pc.COLUMN_NAME) + ',d.' + QUOTENAME(pc.COLUMN_NAME) + ') AS VARCHAR(MAX)) AS [@value] '
FROM #tmpPKColumns AS pc
ORDER BY pc.ORDINAL_POSITION
FOR XML PATH('')
),1,16,'');
DECLARE @pkColsCompare VARCHAR(MAX)=
STUFF
(
(
SELECT 'AND i.' + QUOTENAME(pc.COLUMN_NAME) + '=d.' + QUOTENAME(pc.COLUMN_NAME)
FROM #tmpPKColumns AS pc
ORDER BY pc.ORDINAL_POSITION
FOR XML PATH('')
),1,3,'');
DECLARE @cols VARCHAR(MAX)=
STUFF
(
(
SELECT ',' + CASE WHEN @tp='upd' THEN
'CASE WHEN (i.[' + COLUMN_NAME + ']!=d.[' + COLUMN_NAME + '] ' +
'OR (i.[' + COLUMN_NAME + '] IS NULL AND d.[' + COLUMN_NAME + '] IS NOT NULL) ' +
'OR (i.['+ COLUMN_NAME + '] IS NOT NULL AND d.[' + COLUMN_NAME + '] IS NULL)) ' +
'THEN ' ELSE '' END +
'(SELECT ''' + COLUMN_NAME + ''' AS [@name]' +
CASE WHEN @tp IN ('upd','del') THEN ',ISNULL(CAST(d.[' + COLUMN_NAME + '] AS NVARCHAR(MAX)),N''##NULL##'') AS [@old]' ELSE '' END +
CASE WHEN @tp IN ('ins','upd') THEN ',ISNULL(CAST(i.[' + COLUMN_NAME + '] AS NVARCHAR(MAX)),N''##NULL##'') AS [@new] ' ELSE '' END +
' FOR XML PATH(''Column''),TYPE) ' + CASE WHEN @tp='upd' THEN 'END' ELSE '' END
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA=@tableSchema AND TABLE_NAME=@tableName
FOR XML PATH('')
),1,1,''
);
DECLARE @cmd VARCHAR(MAX)=
'SET LANGUAGE ENGLISH;
WITH ChangedColumns AS
(
SELECT A.PK' +
',A.PK.query(''data(/PK/Column/@value)'').value(''text()[1]'',''nvarchar(max)'') AS PKVals' +
',Col.*
FROM #tmpInserted AS i
FULL OUTER JOIN #tmpDeleted AS d ON ' + @pkColsCompare +
' CROSS APPLY
(
SELECT ' + @cols + '
FOR XML PATH(''''),TYPE
) AS Col([Column])
CROSS APPLY(SELECT (SELECT tbl.* FROM (SELECT ' + @pkCols + ') AS tbl FOR XML PATH(''Column''), ROOT(''PK''),TYPE)) AS A(PK)
)
INSERT INTO AuditTest(ID,LogDate,TableSchema,TableName,AuditType,Content)
SELECT ''' + CAST(@AuditID AS VARCHAR(MAX)) + ''',''' + CONVERT(VARCHAR(MAX),@LogDate,126) + ''',''' + @tableSchema + ''',''' + @tableName + ''',''' + @tp + '''
,(
SELECT ''' + @tableSchema + ''' AS [@TableSchema]
,''' + @tableName + ''' AS [@TableName]
,''' + @tp + ''' AS [@ActionType]
,(
SELECT ChangedColumns.PK AS [*]
,(
SELECT x.[Column] AS [*],''''
FROM ChangedColumns AS x
WHERE x.PKVals=ChangedColumns.PKVals
FOR XML PATH(''Values''),TYPE
)
FROM ChangedColumns
FOR XML PATH(''Row''),TYPE
)
FOR XML PATH(''Changes'')
);';
EXEC (@cmd);
DROP TABLE #tmpInserted;
DROP TABLE #tmpDeleted;
END
GO
--Now let's test it with some operations:
UPDATE dbo.Testx SET Test1='New 1' WHERE ID1={d'2000-01-01'};
UPDATE dbo.Testx SET Test1='New 1',Test2={d'2000-01-01'} ;
DELETE FROM dbo.Testx WHERE ID1={d'2000-02-01'};
DELETE FROM dbo.Testx WHERE ID1=GETDATE(); --no affect
INSERT INTO dbo.Testx(ID1,ID2,Test1,Test2) VALUES
({d'2000-03-01'},NEWID(),'Test3',{d'2001-03-03'})
,({d'2000-04-01'},NEWID(),'Test4',{d'2001-04-04'})
,({d'2000-05-01'},NEWID(),'Test5',{d'2001-05-05'});
UPDATE dbo.Testx SET Test2=NULL; --all rows
DELETE FROM dbo.Testx WHERE ID1 IN ({d'2000-02-01'},{d'2000-03-01'});
GO
--Check the final status
SELECT * FROM dbo.Testx;
SELECT * FROM AuditTest;
GO
--Clean up (carefull with real data!)
DROP TABLE dbo.Testx;
GO
DROP TABLE dbo.AuditTest;
GO
The result of the insert
<Changes TableSchema="dbo" TableName="Testx" ActionType="ins">
<Row>
<PK>
<Column name="ID1" value="May 1 2000 12:00AM" />
<Column name="ID2" value="C2EB4D11-63F8-434E-8470-FB4A422A4ED1" />
</PK>
<Values>
<Column name="ID1" new="May 1 2000 12:00AM" />
<Column name="ID2" new="C2EB4D11-63F8-434E-8470-FB4A422A4ED1" />
<Column name="Test1" new="Test5" />
<Column name="Test2" new="May 5 2001 12:00AM" />
</Values>
</Row>
<Row>
<PK>
<Column name="ID1" value="Apr 1 2000 12:00AM" />
<Column name="ID2" value="28625CE7-9424-4FA6-AEDA-1E4853451655" />
</PK>
<Values>
<Column name="ID1" new="Apr 1 2000 12:00AM" />
<Column name="ID2" new="28625CE7-9424-4FA6-AEDA-1E4853451655" />
<Column name="Test1" new="Test4" />
<Column name="Test2" new="Apr 4 2001 12:00AM" />
</Values>
</Row>
<Row>
<PK>
<Column name="ID1" value="Mar 1 2000 12:00AM" />
<Column name="ID2" value="7AB56E6C-2ADC-4945-9D94-15BC9B3F270C" />
</PK>
<Values>
<Column name="ID1" new="Mar 1 2000 12:00AM" />
<Column name="ID2" new="7AB56E6C-2ADC-4945-9D94-15BC9B3F270C" />
<Column name="Test1" new="Test3" />
<Column name="Test2" new="Mar 3 2001 12:00AM" />
</Values>
</Row>
</Changes>
The selective result of an update
<Changes TableSchema="dbo" TableName="Testx" ActionType="upd">
<Row>
<PK>
<Column name="ID1" value="Feb 1 2000 12:00AM" />
<Column name="ID2" value="D7AB263A-EEFC-47DB-A6BB-A559FE8F2119" />
</PK>
<Values>
<Column name="Test1" old="Test2" new="New 1" />
<Column name="Test2" old="Feb 2 2002 12:00AM" new="Jan 1 2000 12:00AM" />
</Values>
</Row>
<Row>
<PK>
<Column name="ID1" value="Jan 1 2000 12:00AM" />
<Column name="ID2" value="318C0A66-8833-4F03-BCEF-7AB78C91704F" />
</PK>
<Values>
<Column name="Test2" old="##NULL##" new="Jan 1 2000 12:00AM" />
</Values>
</Row>
</Changes>
And the result of a delete
<Changes TableSchema="dbo" TableName="Testx" ActionType="del">
<Row>
<PK>
<Column name="ID1" value="Mar 1 2000 12:00AM" />
<Column name="ID2" value="7AB56E6C-2ADC-4945-9D94-15BC9B3F270C" />
</PK>
<Values>
<Column name="ID1" old="Mar 1 2000 12:00AM" />
<Column name="ID2" old="7AB56E6C-2ADC-4945-9D94-15BC9B3F270C" />
<Column name="Test1" old="Test3" />
<Column name="Test2" old="##NULL##" />
</Values>
</Row>
</Changes>
CREATE TRIGGER TriggerName
ON TableName
FOR INSERT, UPDATE, DELETE AS
BEGIN
SET NOCOUNT ON
DECLARE @ExecStr varchar(50), @Qry nvarchar(255)
CREATE TABLE #inputbuffer
(
EventType nvarchar(30),
Parameters int,
EventInfo nvarchar(255)
)
SET @ExecStr = 'DBCC INPUTBUFFER(' + STR(@@SPID) + ')'
INSERT INTO #inputbuffer
EXEC (@ExecStr)
SET @Qry = (SELECT EventInfo FROM #inputbuffer)
SELECT @Qry AS 'Query that fired the trigger',
SYSTEM_USER as LoginName,
USER AS UserName,
CURRENT_TIMESTAMP AS CurrentTime
END
Trigger is used to If you modify or insert in a particular table this will execute, and you can check the particular column in trigger. Full Example with explanation is in the following website. http://www.allinworld99.blogspot.com/2015/04/triggers-in-sql.html
I have a very similar table to your proposed design that I have used.
I added insert, update and delete triggers to selected tables, and then checked for changes to selected fields. At the time it was simple and works well.
Here are the issues I find with this approach:
The audit table old/new value fields had to be varchar(MAX) types to be able to handle all the different values that could be audited: int,bool,decimal,float,varchar, etc. all have to fit
The code to check for each field is tedious to write an maintain. It's also easy to miss things (like changing a null field to a value didn't get caught, because NULL != value is NULL.
Delete record: how do you record this? All fields? Selected ones? It gets complicated
My future vision is to use some SQL-CLR code and write a generic trigger that is executed and checks table meta-data to see what to audit. Secondly, the New/Old values will be converted to XML fields and the whole object recorded: this results in more data but a delete has a whole record. There are several articles on the web about XML audit triggers.
There is a generic way to do it.
CREATE TABLE [dbo].[Audit](
[TYPE] [CHAR](1) NULL,
[TableName] [VARCHAR](128) NULL,
[PK] [VARCHAR](1000) NULL,
[FieldName] [VARCHAR](128) NULL,
[OldValue] [VARCHAR](1000) NULL,
[NewValue] [VARCHAR](1000) NULL,
[UpdateDate] [datetime] NULL,
[UserName] [VARCHAR](128) NULL
) ON [PRIMARY]
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