Audit information with SQL

Time comes when you have a database running, fully deployed and working, and a few years later something appears to be going wrong but you are not sure what or what is happening.

You start looking at possible options, and one of the first that springs to mind is performing an audit on any changed information, wouldn't it be nice to be able to audit information so that you can see what an when things are changing?

One way of doing this is to use triggers with inside of SQL Server, this does come at a high cost, but does provide you with the information you require.

First we need to have a Audit table

CREATE TABLE [dbo].[Audit](

    [AuditID] [int] IDENTITY(1,1) NOT NULL,

    [Type] [char](1) NULL,

    [TableName] [varchar](128) NULL,

    [PrimaryKeyField] [varchar](1000) NULL,

    [PrimaryKeyValue] [varchar](1000) NULL,

    [FieldName] [varchar](128) NULL,

    [OldValue] [varchar](1000) NULL,

    [NewValue] [varchar](1000) NULL,

    [UpdateDate] [datetime] NULL DEFAULT (getdate()),

    [UserName] [varchar](128) NULL

) ON [PRIMARY]

Okay now that is done, then we need to decide on what triggers we want, we could place a trigger on all the tables, like this:

DECLARE @sql varchar(8000), @TABLE_NAME sysname
SET NOCOUNT ON

SELECT @TABLE_NAME= MIN(TABLE_NAME)
FROM INFORMATION_SCHEMA.Tables
WHERE
TABLE_TYPE= 'BASE TABLE'
AND TABLE_NAME!= 'sysdiagrams'
AND TABLE_NAME!= 'Audit'

WHILE @TABLE_NAME IS NOT NULL
 BEGIN
EXEC('IF OBJECT_ID (''' + @TABLE_NAME+ '_ChangeTracking'', ''TR'') IS NOT NULL DROP TRIGGER ' + @TABLE_NAME+ '_ChangeTracking')
SELECT @sql =
'
create trigger ' + @TABLE_NAME+ '_ChangeTracking on ' + @TABLE_NAME+ ' for insert, update, delete
as

declare @bit int ,
@field int ,
@maxfield int ,
@char int ,
@fieldname varchar(128) ,
@TableName varchar(128) ,
@PKCols varchar(1000) ,
@sql varchar(2000),
@UpdateDate varchar(21) ,
@UserName varchar(128) ,
@Type char(1) ,
@PKFieldSelect varchar(1000),
@PKValueSelect varchar(1000)

select @TableName = ''' + @TABLE_NAME+ '''

-- date and user
select @UserName = system_user ,
@UpdateDate = convert(varchar(8), getdate(), 112) + '' '' + convert(varchar(12), getdate(), 114)

-- Action
if exists (select * from inserted)
if exists (select * from deleted)
select @Type = ''U''
else
select @Type = ''I''
else
select @Type = ''D''

-- get list of columns
select * into #ins from inserted
select * into #del from deleted

-- Get primary key columns for full outer join
select @PKCols = coalesce(@PKCols + '' and'', '' on'') + '' i.'' + c.COLUMN_NAME + '' = d.'' + c.COLUMN_NAME
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,
INFORMATION_SCHEMA.KEY_COLUMN_USAGE c
where pk.TABLE_NAME = @TableName
and CONSTRAINT_TYPE = ''PRIMARY KEY''
and c.TABLE_NAME = pk.TABLE_NAME
and c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME

-- Get primary key fields select for insert
select @PKFieldSelect = coalesce(@PKFieldSelect+''+'','''') + '''''''' + COLUMN_NAME + ''''''''
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,
INFORMATION_SCHEMA.KEY_COLUMN_USAGE c
where pk.TABLE_NAME = @TableName
and CONSTRAINT_TYPE = ''PRIMARY KEY''
and c.TABLE_NAME = pk.TABLE_NAME
and c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME

select
@PKValueSelect = coalesce(@PKValueSelect+''+'','''') +
''convert(varchar(100), coalesce(i.'' + COLUMN_NAME + '',d.'' +
COLUMN_NAME + ''))''
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,  
INFORMATION_SCHEMA.KEY_COLUMN_USAGE c 
where  pk.TABLE_NAME = @TableName 
and CONSTRAINT_TYPE = ''PRIMARY KEY'' 
and c.TABLE_NAME = pk.TABLE_NAME 
and c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME

if @PKCols is null
begin
raiserror(''no PK on table %s'', 16, -1, @TableName)
return
end

select @field = 0, @maxfield = max(ORDINAL_POSITION) from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = @TableName
while @field < @maxfield
begin
select
@field = min(ORDINAL_POSITION) from INFORMATION_SCHEMA.COLUMNS where
TABLE_NAME = @TableName and ORDINAL_POSITION > @field
select @bit = (@field - 1 )% 8 + 1
select @bit = power(2,@bit - 1)
select @char = ((@field - 1) / 8) + 1
if substring(COLUMNS_UPDATED(),@char, 1) & @bit > 0 or @Type in (''I'',''D'')
begin
select @fieldname = COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = @TableName and ORDINAL_POSITION = @field
select
@sql = ''insert Audit (Type, TableName, PrimaryKeyField,
PrimaryKeyValue, FieldName, OldValue, NewValue, UpdateDate, UserName)''
select @sql = @sql + '' select '''''' + @Type + ''''''''
select @sql = @sql + '','''''' + @TableName + ''''''''
select @sql = @sql + '','' + @PKFieldSelect
select @sql = @sql + '','' + @PKValueSelect
select @sql = @sql + '','''''' + @fieldname + ''''''''
select @sql = @sql + '',convert(varchar(1000),d.'' + @fieldname + '')''
select @sql = @sql + '',convert(varchar(1000),i.'' + @fieldname + '')''
select @sql = @sql + '','''''' + @UpdateDate + ''''''''
select @sql = @sql + '','''''' + @UserName + ''''''''
select @sql = @sql + '' from #ins i full outer join #del d''
select @sql = @sql + @PKCols
select @sql = @sql + '' where i.'' + @fieldname + '' <> d.'' + @fieldname
select @sql = @sql + '' or (i.'' + @fieldname + '' is null and  d.'' + @fieldname + '' is not null)''
select @sql = @sql + '' or (i.'' + @fieldname + '' is not null and  d.'' + @fieldname + '' is null)''
exec (@sql)
end
end
'
SELECT @sql
EXEC(@sql)
SELECT @TABLE_NAME= MIN(TABLE_NAME) FROM INFORMATION_SCHEMA.Tables
WHERE TABLE_NAME> @TABLE_NAME
AND TABLE_TYPE= 'BASE TABLE'
AND TABLE_NAME!= 'sysdiagrams'
AND TABLE_NAME!= 'Audit'
END

or just a selected table

 

DECLARE @TABLE varchar(1000)

SET @TABLE = 'table name to audit'

DECLARE @sql varchar(8000), @TABLE_NAME sysname
SET NOCOUNT ON

SELECT @TABLE_NAME= MIN(TABLE_NAME)
FROM INFORMATION_SCHEMA.Tables
WHERE
TABLE_TYPE= 'BASE TABLE'
AND Table_Name = @TABLE

WHILE @TABLE_NAME IS NOT NULL
 BEGIN
EXEC('IF OBJECT_ID (''' + @TABLE_NAME+ '_ChangeTracking'', ''TR'') IS NOT NULL DROP TRIGGER ' + @TABLE_NAME+ '_ChangeTracking')
SELECT @sql =
'
create trigger ' + @TABLE_NAME+ '_ChangeTracking on ' + @TABLE_NAME+ ' for insert, update, delete
as

declare @bit int ,
@field int ,
@maxfield int ,
@char int ,
@fieldname varchar(128) ,
@TableName varchar(128) ,
@PKCols varchar(1000) ,
@sql varchar(2000),
@UpdateDate varchar(21) ,
@UserName varchar(128) ,
@Type char(1) ,
@PKFieldSelect varchar(1000),
@PKValueSelect varchar(1000)

select @TableName = ''' + @TABLE_NAME+ '''

-- date and user
select @UserName = system_user ,
@UpdateDate = convert(varchar(8), getdate(), 112) + '' '' + convert(varchar(12), getdate(), 114)

-- Action
if exists (select * from inserted)
if exists (select * from deleted)
select @Type = ''U''
else
select @Type = ''I''
else
select @Type = ''D''

-- get list of columns
select * into #ins from inserted
select * into #del from deleted

-- Get primary key columns for full outer join
select @PKCols = coalesce(@PKCols + '' and'', '' on'') + '' i.'' + c.COLUMN_NAME + '' = d.'' + c.COLUMN_NAME
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,
INFORMATION_SCHEMA.KEY_COLUMN_USAGE c
where pk.TABLE_NAME = @TableName
and CONSTRAINT_TYPE = ''PRIMARY KEY''
and c.TABLE_NAME = pk.TABLE_NAME
and c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME

-- Get primary key fields select for insert
select @PKFieldSelect = coalesce(@PKFieldSelect+''+'','''') + '''''''' + COLUMN_NAME + ''''''''
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,
INFORMATION_SCHEMA.KEY_COLUMN_USAGE c
where pk.TABLE_NAME = @TableName
and CONSTRAINT_TYPE = ''PRIMARY KEY''
and c.TABLE_NAME = pk.TABLE_NAME
and c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME

select
@PKValueSelect = coalesce(@PKValueSelect+''+'','''') +
''convert(varchar(100), coalesce(i.'' + COLUMN_NAME + '',d.'' +
COLUMN_NAME + ''))''
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,  
INFORMATION_SCHEMA.KEY_COLUMN_USAGE c 
where  pk.TABLE_NAME = @TableName 
and CONSTRAINT_TYPE = ''PRIMARY KEY'' 
and c.TABLE_NAME = pk.TABLE_NAME 
and c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME

if @PKCols is null
begin
raiserror(''no PK on table %s'', 16, -1, @TableName)
return
end

select @field = 0, @maxfield = max(ORDINAL_POSITION) from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = @TableName
while @field < @maxfield
begin
select
@field = min(ORDINAL_POSITION) from INFORMATION_SCHEMA.COLUMNS where
TABLE_NAME = @TableName and ORDINAL_POSITION > @field
select @bit = (@field - 1 )% 8 + 1
select @bit = power(2,@bit - 1)
select @char = ((@field - 1) / 8) + 1
if substring(COLUMNS_UPDATED(),@char, 1) & @bit > 0 or @Type in (''I'',''D'')
begin
select @fieldname = COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = @TableName and ORDINAL_POSITION = @field
select
@sql = ''insert Audit (Type, TableName, PrimaryKeyField,
PrimaryKeyValue, FieldName, OldValue, NewValue, UpdateDate, UserName)''
select @sql = @sql + '' select '''''' + @Type + ''''''''
select @sql = @sql + '','''''' + @TableName + ''''''''
select @sql = @sql + '','' + @PKFieldSelect
select @sql = @sql + '','' + @PKValueSelect
select @sql = @sql + '','''''' + @fieldname + ''''''''
select @sql = @sql + '',convert(varchar(1000),d.'' + @fieldname + '')''
select @sql = @sql + '',convert(varchar(1000),i.'' + @fieldname + '')''
select @sql = @sql + '','''''' + @UpdateDate + ''''''''
select @sql = @sql + '','''''' + @UserName + ''''''''
select @sql = @sql + '' from #ins i full outer join #del d''
select @sql = @sql + @PKCols
select @sql = @sql + '' where i.'' + @fieldname + '' <> d.'' + @fieldname
select @sql = @sql + '' or (i.'' + @fieldname + '' is null and  d.'' + @fieldname + '' is not null)''
select @sql = @sql + '' or (i.'' + @fieldname + '' is not null and  d.'' + @fieldname + '' is null)''
exec (@sql)
end
end
'
SELECT @sql
EXEC(@sql)
SELECT @TABLE_NAME= MIN(TABLE_NAME) FROM INFORMATION_SCHEMA.Tables
WHERE TABLE_NAME> @TABLE_NAME
AND TABLE_TYPE= 'BASE TABLE'
AND Table_Name = @TABLE
END

Of course you need someway of turning off the triggers, so here you are:

 

DECLARE @sql varchar(8000), @TABLE_NAME sysname

SET NOCOUNT ON



SELECT @TABLE_NAME= MIN(TABLE_NAME)

FROM INFORMATION_SCHEMA.Tables

WHERE

TABLE_TYPE= 'BASE TABLE'

AND TABLE_NAME!= 'sysdiagrams'

AND TABLE_NAME!= 'Audit'



WHILE @TABLE_NAME IS NOT NULL

 BEGIN

EXEC('IF OBJECT_ID (''' + @TABLE_NAME+ '_ChangeTracking'', ''TR'') IS NOT NULL DROP TRIGGER ' + @TABLE_NAME+ '_ChangeTracking')

SELECT @sql =

'

DROP trigger ' + @TABLE_NAME+ '_ChangeTracking'



SELECT @sql

EXEC(@sql)

SELECT @TABLE_NAME= MIN(TABLE_NAME) FROM INFORMATION_SCHEMA.Tables

WHERE TABLE_NAME> @TABLE_NAME

AND TABLE_TYPE= 'BASE TABLE'

AND TABLE_NAME!= 'sysdiagrams'

AND TABLE_NAME!= 'Audit'

END

That should do it, I got the majority of SQL from Jon Galloway post Adding simple trigger-based auditing to your SQL Server database, so I can;t take all the credit for these scripts, just the changes and modifications.

If performance is an issue they you could check out Centralized Asynchronous Auditing with Service Broker or Centralized Asynchronous Auditing across Instances and Servers with Service Broker

blog comments powered by Disqus

About the author

You have probably figured out by now that my name is Bryan Avery (if not, please refer to your browser's address field).  Technology is more than a career to me - it is both a hobby and a passion.  I'm an ASP.NET/C# Developer at heart...

Month List