SQL Server auto audit updated column

Question

I need to create a trigger on SQL Server to write only updated column into an audit table with table name, column name, previous/new value, date, time and user for specific

Answer 1

i normally have a table like this to store the audit data and i got this solution from here https://www.simple-talk.com/sql/database-administration/pop-rivetts-sql-server-faq-no.5-pop-on-the-audit-trail/

    CREATE TABLE [dbo].[Audit](
    [AuditID] [int] IDENTITY(1,1) NOT NULL,
    [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,
 CONSTRAINT [PK_Audit] PRIMARY KEY CLUSTERED 
(
    [AuditID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

And then add the below trigger to every table i want to audit

CREATE TRIGGER [dbo].[Tr_DB_Audit] ON [dbo].['YourTableName'] 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) ,
       @PKSelect VARCHAR(1000)


--You will need to change @TableName to match the table to be audited
SELECT @TableName = 'NameOfTableYouWantToAudit'

-- 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 select for insert
SELECT @PKSelect = COALESCE(@PKSelect+'+','') 
       + '''<' + COLUMN_NAME 
       + '=''+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, 
               PK, 
               FieldName, 
               OldValue, 
               NewValue, 
               UpdateDate, 
               UserName)
select ''' + @Type + ''',''' 
       + @TableName + ''',' + @PKSelect
       + ',''' + @fieldname + ''''
       + ',convert(varchar(1000),d.' + @fieldname + ')'
       + ',convert(varchar(1000),i.' + @fieldname + ')'
       + ',''' + @UpdateDate + ''''
       + ',''' + @UserName + ''''
       + ' from #ins i full outer join #del d'
       + @PKCols
       + ' where i.' + @fieldname + ' <> d.' + @fieldname 
       + ' or (i.' + @fieldname + ' is null and  d.'
                                + @fieldname
                                + ' is not null)' 
       + ' or (i.' + @fieldname + ' is not null and  d.' 
                                + @fieldname
                                + ' is null)' 
               EXEC (@sql)
       END
END

You could also have a look at this article http://weblogs.asp.net/jgalloway/archive/2008/01/27/adding-simple-trigger-based-auditing-to-your-sql-server-database.aspx

Answer 2

We’re using third party tool ApexSQL Audit to generate audit triggers since we have a lot of tables that require auditing.

If you don’t need a third party tool you can use this in trial mode and see how they are implementing triggers and storage tables.

Below is a sample trigger and storage tables I picked up quickly from my database.

Data storage table:

Table that stores details about transactions:

Here is a sample of delete trigger. Note the comment inline

CREATE TRIGGER [dbo].[tr_d_AUDIT_Table_Name]
ON [dbo].[Table_Name]
FOR DELETE
NOT FOR REPLICATION
AS

BEGIN
    DECLARE 
        @IDENTITY_SAVE              varchar(50),
        @AUDIT_LOG_TRANSACTION_ID       Int,
        @PRIM_KEY               nvarchar(4000),
        @ROWS_COUNT             int

    SET NOCOUNT ON


    Select @ROWS_COUNT=count(*) from deleted
    Set @IDENTITY_SAVE = CAST(IsNull(@@IDENTITY,1) AS varchar(50))

    INSERT
    INTO dbo.AUDIT_LOG_TRANSACTIONS
    (
        TABLE_NAME,
        TABLE_SCHEMA,
        AUDIT_ACTION_ID,
        HOST_NAME,
        APP_NAME,
        MODIFIED_BY,
        MODIFIED_DATE,
        AFFECTED_ROWS,
        [DATABASE]
    )
    values(
        'Table_Name',
        'dbo',
        3,  
        CASE 
          WHEN LEN(HOST_NAME()) < 1 THEN ' '
          ELSE HOST_NAME()
        END,
        CASE 
          WHEN LEN(APP_NAME()) < 1 THEN ' '
          ELSE APP_NAME()
        END,
        SUSER_SNAME(),
        GETDATE(),
        @ROWS_COUNT,
        'database_name'
    )

    Set @AUDIT_LOG_TRANSACTION_ID = SCOPE_IDENTITY()

    INSERT
    INTO dbo.AUDIT_LOG_DATA
    (
        AUDIT_LOG_TRANSACTION_ID,
        PRIMARY_KEY_DATA,
        COL_NAME,
        OLD_VALUE_LONG,
        DATA_TYPE
        , KEY1
    )
    SELECT
        @AUDIT_LOG_TRANSACTION_ID,
        convert(nvarchar(1500), IsNull('[Order_ID]='+CONVERT(nvarchar(4000), OLD.[Order_ID], 0), '[Order_ID] Is Null')),
        'Order_ID',
        CONVERT(nvarchar(4000), OLD.[Order_ID], 0),
        'A'
        ,  CONVERT(nvarchar(500), CONVERT(nvarchar(4000), OLD.[Order_ID], 0))
    FROM deleted OLD
    WHERE
        OLD.[Order_ID] Is Not Null

    /*
       Insert statement above is replicated for each column being audited
     */

END