SQL Server Update Trigger, Get Only modified field

2019-01-10 23:51发布

站内问答 / SQL-Server
485 6 4

I am aware of COLUMNS_UPDATED, well I need some quick shortcut (if anyone has made, I am already making one, but if anyone can save my time, I will appriciate it)

I need basicaly an XML of only updated column values, I need this for replication purpose.

SELECT * FROM inserted gives me each column, but I need only updated ones.

something like following...

CREATE TRIGGER DBCustomers_Insert
    ON DBCustomers
    AFTER UPDATE
AS
BEGIN
    DECLARE @sql as NVARCHAR(1024);
    SET @sql = 'SELECT ';


    I NEED HELP FOR FOLLOWING LINE ...., I can manually write every column, but I need 
    an automated routin which can work regardless of column specification
    for each column, if its modified append $sql = ',' + columnname...

    SET @sql = $sql + ' FROM inserted FOR XML RAW';

    DECLARE @x as XML;
    SET @x = CAST(EXEC(@sql) AS XML);


    .. use @x

END

6条回答
迷人小祖宗
2楼-- · 2019-01-11 00:09

The below code works for over 64 columns and logs only the updated columns. Follow the instruction in the comments and all should be well.

/*******************************************************************************************
 *         Add the below table to your database to track data changes using the trigger    *
 *         below. Remember to change the variables in the trigger to match the table that  *
 *         will be firing the trigger                                                      *
 *******************************************************************************************/
SET ANSI_NULLS ON;
GO

SET QUOTED_IDENTIFIER ON;
GO

CREATE TABLE [dbo].[AuditDataChanges]
(
  [RecordId] [INT] IDENTITY(1, 1)
                   NOT NULL ,
  [TableName] [VARCHAR](50) NOT NULL ,
  [RecordPK] [VARCHAR](50) NOT NULL ,
  [ColumnName] [VARCHAR](50) NOT NULL ,
  [OldValue] [VARCHAR](50) NULL ,
  [NewValue] [VARCHAR](50) NULL ,
  [ChangeDate] [DATETIME2](7) NOT NULL ,
  [UpdatedBy] [VARCHAR](50) NOT NULL ,
  CONSTRAINT [PK_AuditDataChanges] PRIMARY KEY CLUSTERED
    ( [RecordId] ASC )
    WITH ( PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
           IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
           ALLOW_PAGE_LOCKS = ON ) ON [PRIMARY]
)
ON  [PRIMARY];

GO

ALTER TABLE [dbo].[AuditDataChanges] ADD  CONSTRAINT [DF_AuditDataChanges_ChangeDate]  DEFAULT (GETDATE()) FOR [ChangeDate];
GO



/************************************************************************************************
 * Add the below trigger to any table you want to audit data changes on. Changes will be saved  *
 * in the AuditChangesTable.                                                                    *
 ************************************************************************************************/


ALTER TRIGGER trg_Survey_Identify_Updated_Columns ON Survey --Change to match your table name
   FOR INSERT, UPDATE
AS
SET NOCOUNT ON;

DECLARE @sql VARCHAR(5000) ,
    @sqlInserted NVARCHAR(500) ,
    @sqlDeleted NVARCHAR(500) ,
    @NewValue NVARCHAR(100) ,
    @OldValue NVARCHAR(100) ,
    @UpdatedBy VARCHAR(50) ,
    @ParmDefinitionD NVARCHAR(500) ,
    @ParmDefinitionI NVARCHAR(500) ,
    @TABLE_NAME VARCHAR(100) ,
    @COLUMN_NAME VARCHAR(100) ,
    @modifiedColumnsList NVARCHAR(4000) ,
    @ColumnListItem NVARCHAR(500) ,
    @Pos INT ,
    @RecordPk VARCHAR(50) ,
    @RecordPkName VARCHAR(50);

SELECT  *
INTO    #deleted
FROM    deleted;
SELECT  *
INTO    #Inserted
FROM    inserted;

SET @TABLE_NAME = 'Survey'; ---Change to your table name
SELECT  @UpdatedBy = UpdatedBy --Change to your column name for the user update field
FROM    inserted;
SELECT  @RecordPk = SurveyId --Change to the table primary key field
FROM    inserted;   
SET @RecordPkName = 'SurveyId';
SET @modifiedColumnsList = STUFF(( SELECT   ',' + name
                                   FROM     sys.columns
                                   WHERE    object_id = OBJECT_ID(@TABLE_NAME)
                                            AND SUBSTRING(COLUMNS_UPDATED(),
                                                          ( ( column_id
                                                          - 1 ) / 8 + 1 ),
                                                          1) & ( POWER(2,
                                                          ( ( column_id
                                                          - 1 ) % 8 + 1 )
                                                          - 1) ) = POWER(2,
                                                          ( column_id - 1 )
                                                          % 8)
                                 FOR
                                   XML PATH('')
                                 ), 1, 1, '');


WHILE LEN(@modifiedColumnsList) > 0
    BEGIN
        SET @Pos = CHARINDEX(',', @modifiedColumnsList);
        IF @Pos = 0
            BEGIN
                SET @ColumnListItem = @modifiedColumnsList;
            END;
        ELSE
            BEGIN
                SET @ColumnListItem = SUBSTRING(@modifiedColumnsList, 1,
                                                @Pos - 1);
            END;    

        SET @COLUMN_NAME = @ColumnListItem;
        SET @ParmDefinitionD = N'@OldValueOut NVARCHAR(100) OUTPUT';
        SET @ParmDefinitionI = N'@NewValueOut NVARCHAR(100) OUTPUT';
        SET @sqlDeleted = N'SELECT @OldValueOut=' + @COLUMN_NAME
            + ' FROM #deleted where ' + @RecordPkName + '='
            + CONVERT(VARCHAR(50), @RecordPk);
        SET @sqlInserted = N'SELECT @NewValueOut=' + @COLUMN_NAME
            + ' FROM #Inserted where ' + @RecordPkName + '='
            + CONVERT(VARCHAR(50), @RecordPk);
        EXECUTE sp_executesql @sqlDeleted, @ParmDefinitionD,
            @OldValueOut = @OldValue OUTPUT;
        EXECUTE sp_executesql @sqlInserted, @ParmDefinitionI,
            @NewValueOut = @NewValue OUTPUT;
        IF ( LTRIM(RTRIM(@NewValue)) != LTRIM(RTRIM(@OldValue)) )
            BEGIN   
                SET @sql = 'INSERT INTO [dbo].[AuditDataChanges]
                                               ([TableName]
                                               ,[RecordPK]
                                               ,[ColumnName]
                                               ,[OldValue]
                                               ,[NewValue]
                                               ,[UpdatedBy])
                                         VALUES
                                               (' + QUOTENAME(@TABLE_NAME, '''') + '
                                               ,' + QUOTENAME(@RecordPk, '''') + '
                                               ,' + QUOTENAME(@COLUMN_NAME, '''') + '
                                               ,' + QUOTENAME(@OldValue, '''') + '
                                               ,' + QUOTENAME(@NewValue, '''') + '
                                               ,' + QUOTENAME(@UpdatedBy, '''') + ')';


                EXEC (@sql);
            END;     
        SET @COLUMN_NAME = '';
        SET @NewValue = '';
        SET @OldValue = '';
        IF @Pos = 0
            BEGIN
                SET @modifiedColumnsList = '';
            END;
        ELSE
            BEGIN
           -- start substring at the character after the first comma
                SET @modifiedColumnsList = SUBSTRING(@modifiedColumnsList,
                                                     @Pos + 1,
                                                     LEN(@modifiedColumnsList)
                                                     - @Pos);
            END;
    END;
DROP TABLE #Inserted;
DROP TABLE #deleted;

GO
查看更多
0人赞 添加讨论(0) 举报
女痞
3楼-- · 2019-01-11 00:19

Inside the trigger, you can use COLUMNS_UPDATED() like this in order to get updated value

-- Get the table id of the trigger
--
DECLARE @idTable      INT

SELECT  @idTable = T.id 
FROM    sysobjects P JOIN sysobjects T ON P.parent_obj = T.id 
WHERE   P.id = @@procid

-- Get COLUMNS_UPDATED if update
--
DECLARE @Columns_Updated VARCHAR(50)

SELECT  @Columns_Updated = ISNULL(@Columns_Updated + ', ', '') + name 
FROM    syscolumns 
WHERE   id = @idTable   
AND     CONVERT(VARBINARY,REVERSE(COLUMNS_UPDATED())) & POWER(CONVERT(BIGINT, 2), colorder - 1) > 0

But this snipet of code fails when you have a table with more than 62 columns.. Arth.Overflow...

Here is the final version which handles more than 62 columns but give only the number of the updated columns. It's easy to link with 'syscolumns' to get the name

DECLARE @Columns_Updated VARCHAR(100)
SET     @Columns_Updated = ''   

DECLARE @maxByteCU INT
DECLARE @curByteCU INT
SELECT  @maxByteCU = DATALENGTH(COLUMNS_UPDATED()), 
        @curByteCU = 1

WHILE @curByteCU <= @maxByteCU BEGIN
    DECLARE @cByte INT
    SET     @cByte = SUBSTRING(COLUMNS_UPDATED(), @curByteCU, 1)

    DECLARE @curBit INT
    DECLARE @maxBit INT
    SELECT  @curBit = 1, 
            @maxBit = 8
    WHILE @curBit <= @maxBit BEGIN
        IF CONVERT(BIT, @cByte & POWER(2,@curBit - 1)) <> 0 
            SET @Columns_Updated = @Columns_Updated + '[' + CONVERT(VARCHAR, 8 * (@curByteCU - 1) + @curBit) + ']'
        SET @curBit = @curBit + 1
    END
    SET @curByteCU = @curByteCU + 1
END
查看更多
0人赞 添加讨论(0) 举报
ら.Afraid
4楼-- · 2019-01-11 00:21

The sample code provided by Rick lack handling for multiple rows update.

Please let me enhance Rick's version as below:

USE [AFC]
GO

/****** Object:  Trigger [dbo].[trg_Survey_Identify_Updated_Columns]    Script Date: 27/7/2018 14:08:49 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

ALTER TRIGGER [dbo].[trg_Survey_Identify_Updated_Columns] ON [dbo].[Sample_Table] --Change to match your table name
FOR INSERT
	,UPDATE
AS
SET NOCOUNT ON;

DECLARE @sql VARCHAR(5000)
	,@sqlInserted NVARCHAR(500)
	,@sqlDeleted NVARCHAR(500)
	,@NewValue NVARCHAR(100)
	,@OldValue NVARCHAR(100)
	,@UpdatedBy VARCHAR(50)
	,@ParmDefinitionD NVARCHAR(500)
	,@ParmDefinitionI NVARCHAR(500)
	,@TABLE_NAME VARCHAR(100)
	,@COLUMN_NAME VARCHAR(100)
	,@modifiedColumnsList NVARCHAR(4000)
	,@ColumnListItem NVARCHAR(500)
	,@Pos INT
	,@RecordPk VARCHAR(50)
	,@RecordPkName VARCHAR(50);

SELECT *
INTO #deleted
FROM deleted;

SELECT *
INTO #Inserted
FROM inserted;

SET @TABLE_NAME = 'Sample_Table';---Change to your table name

DECLARE t_cursor CURSOR
FOR
SELECT ContactID 
FROM inserted

OPEN t_cursor

FETCH NEXT
FROM t_cursor
INTO @RecordPk 

WHILE @@FETCH_STATUS = 0
BEGIN
	--SELECT @UpdatedBy = Surname --Change to your column name for the user update field
	--FROM inserted;
	--SELECT @RecordPk = ContactID --Change to the table primary key field
	--FROM inserted;
	SET @RecordPkName = 'ContactID';
	SET @modifiedColumnsList = STUFF((
				SELECT ',' + name
				FROM sys.columns
				WHERE object_id = OBJECT_ID(@TABLE_NAME)
					AND SUBSTRING(COLUMNS_UPDATED(), ((column_id - 1) / 8 + 1), 1) & (POWER(2, ((column_id - 1) % 8 + 1) - 1)) = POWER(2, (column_id - 1) % 8)
				FOR XML PATH('')
				), 1, 1, '');

	WHILE LEN(@modifiedColumnsList) > 0
	BEGIN
		SET @Pos = CHARINDEX(',', @modifiedColumnsList);

		IF @Pos = 0
		BEGIN
			SET @ColumnListItem = @modifiedColumnsList;
		END;
		ELSE
		BEGIN
			SET @ColumnListItem = SUBSTRING(@modifiedColumnsList, 1, @Pos - 1);
		END;

		SET @COLUMN_NAME = @ColumnListItem;
		SET @ParmDefinitionD = N'@OldValueOut NVARCHAR(100) OUTPUT';
		SET @ParmDefinitionI = N'@NewValueOut NVARCHAR(100) OUTPUT';
		SET @sqlDeleted = N'SELECT @OldValueOut=' + @COLUMN_NAME + ' FROM #deleted where ' + @RecordPkName + '=' + CONVERT(VARCHAR(50), @RecordPk);
		SET @sqlInserted = N'SELECT @NewValueOut=' + @COLUMN_NAME + ' FROM #Inserted where ' + @RecordPkName + '=' + CONVERT(VARCHAR(50), @RecordPk);

		EXECUTE sp_executesql @sqlDeleted
			,@ParmDefinitionD
			,@OldValueOut = @OldValue OUTPUT;

		EXECUTE sp_executesql @sqlInserted
			,@ParmDefinitionI
			,@NewValueOut = @NewValue OUTPUT;

		--PRINT @newvalue
		--PRINT @oldvalue

		IF (LTRIM(RTRIM(@NewValue)) != LTRIM(RTRIM(@OldValue)))
		BEGIN
			SET @sql = 'INSERT INTO [dbo].[AuditDataChanges]
                                               ([TableName]
                                               ,[RecordPK]
                                               ,[ColumnName]
                                               ,[OldValue]
                                               ,[NewValue] )
                                         VALUES
                                               (' + QUOTENAME(@TABLE_NAME, '''') + '
                                               ,' + QUOTENAME(@RecordPk, '''') + '
                                               ,' + QUOTENAME(@COLUMN_NAME, '''') + '
                                               ,' + QUOTENAME(@OldValue, '''') + '
                                               ,' + QUOTENAME(@NewValue, '''') + '
                                               '  + ')';

			EXEC (@sql);
		END;

		SET @COLUMN_NAME = '';
		SET @NewValue = '';
		SET @OldValue = '';

		IF @Pos = 0
		BEGIN
			SET @modifiedColumnsList = '';
		END;
		ELSE
		BEGIN
			-- start substring at the character after the first comma
			SET @modifiedColumnsList = SUBSTRING(@modifiedColumnsList, @Pos + 1, LEN(@modifiedColumnsList) - @Pos);
		END;
	END;

	FETCH NEXT
	FROM t_cursor
	INTO @RecordPk 
END

DROP TABLE #Inserted;

DROP TABLE #deleted;

CLOSE t_cursor;

DEALLOCATE t_cursor;

查看更多
0人赞 添加讨论(0) 举报
smile是对你的礼貌
5楼-- · 2019-01-11 00:24

The only way that occurs to me that you could accomplish this without hard coding column names would be to drop the contents of the deleted table to a temp table, then build a query based on the table definition to to compare the contents of your temp table and the actual table, and return a delimited column list based on whether they do or do not match. Admittedly, the below is elaborate. 

Declare @sql nvarchar(4000)
DECLARE @ParmDefinition nvarchar(500)
Declare @OutString varchar(8000)
Declare @tbl sysname

Set @OutString = ''
Set @tbl = 'SomeTable' --The table we are interested in
--Store the contents of deleted in temp table
Select * into #tempDelete from deleted 
--Build sql string based on definition 
--of table 
--to retrieve the column name
--or empty string
--based on comparison between
--target table and temp table
set @sql = ''
Select @sql = @sql + 'Case when IsNull(i.[' + Column_Name + 
'],0) = IsNull(d.[' + Column_name + '],0) then '''' 
 else ' + quotename(Column_Name, char(39)) + ' + '',''' + ' end +'
from information_schema.columns 
where table_name = @tbl
--Define output parameter
set @ParmDefinition = '@OutString varchar(8000) OUTPUT'
--Format sql
set @sql = 'Select @OutString = ' 
+ Substring(@sql,1 , len(@sql) -1) + 
' From SomeTable i  ' --Will need to be updated for target schema
+ ' inner join #tempDelete d on
i.PK = d.PK ' --Will need to be updated for target schema
--Execute sql and retrieve desired column list in output parameter
exec sp_executesql @sql, @ParmDefinition, @OutString OUT
drop table  #tempDelete
--strip trailing column if a non-zero length string 
--was returned
if Len(@Outstring) > 0 
    Set @OutString = Substring(@OutString, 1, Len(@Outstring) -1)
--return comma delimited list of changed columns. 
Select @OutString 
End
查看更多
0人赞 添加讨论(0) 举报
做个烂人
6楼-- · 2019-01-11 00:26

I've another completely different solution that doesn't use COLUMNS_UPDATED at all, nor does it rely on building dynamic SQL at runtime. (You might want to use dynamic SQL at design time but thats another story.)

Basically you start with the inserted and deleted tables, unpivot each of them so you are just left with the unique key, field value and field name columns for each. Then you join the two and filter for anything that's changed.

Here is a full working example, including some test calls to show what is logged.

-- -------------------- Setup tables and some initial data --------------------
CREATE TABLE dbo.Sample_Table (ContactID int, Forename varchar(100), Surname varchar(100), Extn varchar(16), Email varchar(100), Age int );
INSERT INTO Sample_Table VALUES (1,'Bob','Smith','2295','bs@example.com',24);
INSERT INTO Sample_Table VALUES (2,'Alice','Brown','2255','ab@example.com',32);
INSERT INTO Sample_Table VALUES (3,'Reg','Jones','2280','rj@example.com',19);
INSERT INTO Sample_Table VALUES (4,'Mary','Doe','2216','md@example.com',28);
INSERT INTO Sample_Table VALUES (5,'Peter','Nash','2214','pn@example.com',25);

CREATE TABLE dbo.Sample_Table_Changes (ContactID int, FieldName sysname, FieldValueWas sql_variant, FieldValueIs sql_variant, modified datetime default (GETDATE()));

GO

-- -------------------- Create trigger --------------------
CREATE TRIGGER TriggerName ON dbo.Sample_Table FOR DELETE, INSERT, UPDATE AS
BEGIN
    SET NOCOUNT ON;
    --Unpivot deleted
    WITH deleted_unpvt AS (
        SELECT ContactID, FieldName, FieldValue
        FROM 
           (SELECT ContactID
                , cast(Forename as sql_variant) Forename
                , cast(Surname as sql_variant) Surname
                , cast(Extn as sql_variant) Extn
                , cast(Email as sql_variant) Email
                , cast(Age as sql_variant) Age
           FROM deleted) p
        UNPIVOT
           (FieldValue FOR FieldName IN 
              (Forename, Surname, Extn, Email, Age)
        ) AS deleted_unpvt
    ),
    --Unpivot inserted
    inserted_unpvt AS (
        SELECT ContactID, FieldName, FieldValue
        FROM 
           (SELECT ContactID
                , cast(Forename as sql_variant) Forename
                , cast(Surname as sql_variant) Surname
                , cast(Extn as sql_variant) Extn
                , cast(Email as sql_variant) Email
                , cast(Age as sql_variant) Age
           FROM inserted) p
        UNPIVOT
           (FieldValue FOR FieldName IN 
              (Forename, Surname, Extn, Email, Age)
        ) AS inserted_unpvt
    )

    --Join them together and show what's changed
    INSERT INTO Sample_Table_Changes (ContactID, FieldName, FieldValueWas, FieldValueIs)
    SELECT Coalesce (D.ContactID, I.ContactID) ContactID
        , Coalesce (D.FieldName, I.FieldName) FieldName
        , D.FieldValue as FieldValueWas
        , I.FieldValue AS FieldValueIs 
    FROM 
        deleted_unpvt d

            FULL OUTER JOIN 
        inserted_unpvt i
            on      D.ContactID = I.ContactID 
                AND D.FieldName = I.FieldName
    WHERE
         D.FieldValue <> I.FieldValue --Changes
        OR (D.FieldValue IS NOT NULL AND I.FieldValue IS NULL) -- Deletions
        OR (D.FieldValue IS NULL AND I.FieldValue IS NOT NULL) -- Insertions
END
GO
-- -------------------- Try some changes --------------------
UPDATE Sample_Table SET age = age+1;
UPDATE Sample_Table SET Extn = '5'+Extn where Extn Like '221_';

DELETE FROM Sample_Table WHERE ContactID = 3;

INSERT INTO Sample_Table VALUES (6,'Stephen','Turner','2299','st@example.com',25);

UPDATE Sample_Table SET ContactID = 7 where ContactID = 4; --this will be shown as a delete and an insert
-- -------------------- See the results --------------------
SELECT *, SQL_VARIANT_PROPERTY(FieldValueWas, 'BaseType') FieldBaseType, SQL_VARIANT_PROPERTY(FieldValueWas, 'MaxLength') FieldMaxLength from Sample_Table_Changes;

-- -------------------- Cleanup --------------------
DROP TABLE dbo.Sample_Table; DROP TABLE dbo.Sample_Table_Changes;

So no messing around with bigint bitfields and arth overflow problems. If you know the columns you want to compare at design time then you don't need any dynamic SQL.

On the downside the output is in a different format and all the field values are converted to sql_variant, the first could be fixed by pivoting the output again, and the second could be fixed by recasting back to the required types based on your knowledge of the design of the table, but both of these would require some complex dynamic sql. Both of these might not be an issue in your XML output. This question does something similar to getting the output back in the same format.

Edit: Reviewing the comments below, if you have a natural primary key that could change then you can still use this method. You just need to add a column that is populated by default with a GUID using the NEWID() function. You then use this column in place of the primary key.

You may want to add an index to this field, but as the deleted and inserted tables in a trigger are in memory it might not get used and may have a negative effect on performance.

查看更多
0人赞 添加讨论(0) 举报
Lonely孤独者°
7楼-- · 2019-01-11 00:27

I've done it as simple "one-liner". Without using, pivot, loops, many variables etc. that makes it looking like procedural programming. SQL should be used to process data sets :-), the solution is:

DECLARE @sql as NVARCHAR(1024);

select @sql = coalesce(@sql + ',' + quotename(column_name), quotename(column_name))
from INFORMATION_SCHEMA.COLUMNS
where substring(columns_updated(), columnproperty(object_id(table_schema + '.' + table_name, 'U'), column_name, 'columnId') / 8 + 1, 1) & power(2, -1 + columnproperty(object_id(table_schema + '.' + table_name, 'U'), column_name, 'columnId') % 8 ) > 0
    and table_name = 'DBCustomers'
    -- and column_name in ('c1', 'c2') -- limit to specific columns
    -- and column_name not in ('c3', 'c4') -- or exclude specific columns

SET @sql = 'SELECT ' + @sql + ' FROM inserted FOR XML RAW';

DECLARE @x as XML;
SET @x = CAST(EXEC(@sql) AS XML);

It uses COLUMNS_UPDATED, takes care of more than eight columns - it handles as many columns as you want.

It takes care on proper columns order which should be get using COLUMNPROPERTY.

It is based on view COLUMNS so it may include or exclude only specific columns.

查看更多
0人赞 添加讨论(0) 举报
登录 后发表回答
相关问题
查看全部
相关文章
查看全部
收藏的人(4)