How To Create Generic SQL Server Stored Procedure To Perform Inserts Into Audit Table Based on Inserted and Deleted In Trigger

Question

I have implemented an audit trail framework based on the information provided by the first answer to the following post:

SQL Server history table - populate through

Answer 1

We've solved that problem in the following way.

select <list of tracked columns here> into #deleted from deleted;

declare /*const*/ @TABLE_NAME sysname = '[table name]';

declare f cursor
local
forward_only
read_only
for
  select c.name, quotename(c.name, '[')
  from
    sys.columns c
    inner join sys.types t on c.system_type_id = t.system_type_id
  where
    c.object_id = object_id(@TABLE_NAME)
    and c.is_computed = 0
    and c.is_identity = 0
    and t.name not in ('text', 'image', 'timestamp', 'xml')
    and (substring(COLUMNS_UPDATED(), ((c.column_id - 1) / 8) + 1, 1) & power(2, (c.column_id - 1) % 8)) > 0
  ;

declare @field_name sysname, @field_name_sanitised sysname;
create table #results (row_id int not null, field_name sysname not null, oldval nvarchar(150) null, newval nvarchar(150) null);

-- For each changed field, insert what exactly changed into #results

open f;

fetch next from f into @field_name, @field_name_sanitised;
while @@fetch_status = 0
begin
  declare @query nvarchar(4000);

  set @query =  N'insert into #results(row_id, field_name, oldval, newval)
                  select d.row_id, @field_name, d.' + @field_name_sanitised + N', i.' + @field_name_sanitised + N'
                  from
                    #deleted d inner join ' + @TABLE_NAME + N' i on d.row_id = i.row_id
                  where
                    (d.' + @field_name_sanitised + N' <> i.' + @field_name_sanitised + N')
                    or
                    (case when d.' + @field_name_sanitised + N' is null then 1 else 0 end <> case when i.' + @field_name_sanitised + N' is null then 1 else 0 end);'
                ;    

  exec sp_executesql
    @stmt = @query,
    @params = N'@field_name sysname',
    @field_name = @field_name
  ;

  fetch next from f into @field_name, @field_name_sanitised;
end;

close f;
deallocate f;

-- Do something meaningful to #results here

Related reading:

• COLUMNS_UPDATED
• sys.columns

Answer 2

Ran into a similar problem... figured it out this way... may not be the most elegant solution but works for the compliance guys... So here goes...

Based on the solution given here

The xml is extracted with FOR XML from the trigger that updated the table... The "OldValues" come from the DELETED table and the "NewValues" from the INSERTED table... so the final xml looks like this...

            DECLARE @x XML= '<FieldData>
              <UpdatedColumns>
                <trType>OldValues</trType>
                <ID>5</ID>
                <def_label>TEST_TIE</def_label>
                <def_code />
              </UpdatedColumns>
              <UpdatedColumns>
                <trType>OldValues</trType>
                <ID>4</ID>
                <def_label>RP_TIE</def_label>
                <def_code />
              </UpdatedColumns>
              <UpdatedColumns>
                <trType>OldValues</trType>
                <ID>3</ID>
                <def_label>ERR_TIE</def_label>
                <def_code />
              </UpdatedColumns><UpdatedColumns>
                <trType>NewValues</trType>
                <ID>5</ID>
                <def_label>TEST_TIE</def_label>
                <def_code>A</def_code>
              </UpdatedColumns>
              <UpdatedColumns>
                <trType>NewValues</trType>
                <ID>4</ID>
                <def_label>RP_TIE</def_label>
                <def_code>A</def_code>
              </UpdatedColumns>
              <UpdatedColumns>
                <trType>NewValues</trType>
                <ID>3</ID>
                <def_label>ERR_TIE</def_label>
                <def_code>A</def_code>
              </UpdatedColumns>
            </FieldData>'

            declare @timestamp datetime2= SYSDATETIME()

            select 
                     ID = identity(int,1,1), 
                     T.N.value('local-name(.)', 'nvarchar(100)') as NodeName,
                     T.N.value('../ID[1]','nvarchar(100)') AS table_ID,
                     T.N.value('.', 'nvarchar(100)') as OldValue
            INTO #old
            from @x.nodes('//UpdatedColumns/*') as T(N)
            WHERE T.N.value('../trType[1]', 'nvarchar(100)') ='OldValues'


            select 
                     ID = identity(int,1,1),
                     T.N.value('local-name(.)', 'nvarchar(100)') as NodeName,
                     T.N.value('../ID[1]','nvarchar(100)') AS Table_ID,
                     T.N.value('.', 'nvarchar(100)') as NewValue
            into #new
            from @x.nodes('//UpdatedColumns/*') as T(N)
            WHERE T.N.value('../trType[1]', 'nvarchar(100)') ='NewValues'



            SELECT n.table_ID, n.NodeName, o.OldValue, n.NewValue,@timestamp as transation_time FROM #new n
            left outer JOIN #old o ON n.NodeName = o.NodeName AND n.ID = o.ID 
            WHERE isnull(o.[OldValue],'') <> isnull(n.[newValue],'') AND n.NodeName <> 'trType'



            DROP TABLE #new,#old 
            GO