c# - 在sql server的审计表中记录应用程序用户名

Question

我正在处理。SQL Server我记录了我的一些表活动。所以我创建了一个审计表，如下所示：

IF NOT EXISTS
(SELECT * FROM sysobjects WHERE id = OBJECT_ID(N'[dbo].[Audit]') 
 AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
   CREATE TABLE Audit 
   (Type CHAR(1), 
   TableName VARCHAR(128), 
   PK VARCHAR(1000), 
   FieldName VARCHAR(128), 
   OldValue VARCHAR(1000), 
   NewValue VARCHAR(1000), 
   UpdateDate datetime, 
   UserName VARCHAR(128))
GO

我有一个表“位置”，我在其上创建了触发器来捕获表中的所有活动，如下所示：

ALTER TRIGGER [dbo].[TR_lOCATION_AUDIT] 
ON [dbo].[lOCATION] FOR UPDATE,INSERT,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. 
-- Here we made GUESTS for your example.
SELECT @TableName = 'lOCATION'

-- 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

这工作正常。但我的最后一列是用户名。在这里我想从我的应用程序中获取价值。（谁登录了应用程序）。这个应用程序安装了多台计算机并在同一个数据库上工作，同时记录我正在使用他的应用程序用户名..实际上我想在这里显示该用户名..我如何将该值传递给这里

我如何将一个值从 c# 应用程序传递到这个 .username 列我想显示这个传递的值

任何帮助都是非常可观的..

Answer 1

有两种方法可以做到这一点。

方式：1

只需使用新列 UserName 更改您的表，并在您访问表时插入/更新该列。可以从触发器访问表中插入/更新的值。

方式：2（看起来很疯狂）

您首先创建一个附加表来保存触发器中可访问的数据。

CREATE TABLE [dbo].[TriggerData](
        [GUID] [uniqueidentifier] NOT NULL,
        [USERNAME] [nvarchar](max) NULL
) ON [PRIMARY]

然后，在您的 Sql 查询将数据更新到实际表之前，您将所需的附加信息存储在该表的触发器中可访问。

DECLARE @id uniqueidentifier;
SET @id = NEWID();
INSERT INTO TriggerData VALUES (@id, 'USER NAME');

接下来，将唯一 ID 关联到当前会话。

DECLARE @context_info varbinary(100);
SET @context_info = cast(@id as varbinary(100));
SET CONTEXT_INFO @context_info;

现在，进入触发器，这是您在触发器中访问此信息的方式：

CREATE TRIGGER [dbo].[TriggerName]
   ON  [dbo].[Reservations]
   AFTER INSERT, UPDATE, DELETE
AS
BEGIN
    DECLARE @id uniqueidentifier;
    SELECT @id = CAST(CONTEXT_INFO() as uniqueidentifier);

    DECLARE @USERNAMEnvarchar(MAX);

    SELECT @USERNAME= USERNAME
    FROM TriggerData
    WHERE [GUID] = @id;

    -- More sql statements, use @USERNAME for the external information.

    DELETE FROM TriggerData WHERE [GUID] = @id;
END

将代码放在插入/更新和删除命令之前。

DECLARE @id uniqueidentifier;
SET @id = NEWID();
INSERT INTO TriggerData VALUES (@id, 'USER NAME');

DECLARE @context_info varbinary(100);
SET @context_info = cast(@id as varbinary(100));
SET CONTEXT_INFO @context_info;

Answer 2

@Veera的答案非常适合使用唯一 ID进行审计，SQL Server但正如您提到C#的应用程序，您可以创建一个Static class包含用户名和应用程序所需的任何其他变量的应用程序。

在您的情况下，它将类似于：

public static class UserInfo
{
    public static string UserID;
}

现在在用户使用登录表单登录期间获取用户 ID，

UserInfo.UserID=Textbox1.Text;

然后您可以从代码中的任何位置访问 UserID：

string UserID="";
UserID= UserInfo.UserID

我已经展示了使用和不使用 SP 的两种情况，以从应用程序传递用户 IDC#并将其存储在数据库中

无 SP

Using (SqlConnection sqlconn=new  
SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString))
  {
    DataSet ds=new DataSet()
    byte[] Context_Info;

    sqlconn.open();

     string sql1 = "Select cast('UserID='+CONVERT(varchar(10),@UserID)
     +REPLICATE(' ',128) as varbinary(128)) Context_Info";
     string sql2 = "do Insert / Update / Delete that will fire the trigger";

    using (SqlCommand command = new SqlCommand(sql1,sqlconn))
    {
        //Command 1
        using (SqlDataAdapter da = new SqlDataAdapter(command))
        {
            da.Fill(ds);
            Context_Info=(byte[])ds.Tables[0].Rows[0]["Context_Info"];
        }

    } 
   using (Sqlcommand cmd=new Sqlcommand(sql1,sqlConn))
   {
      //Pass both context info and User id
     cmd.Parameters.AddWithValue("@ContextInfo ",ContextInfo);
     cmd.Parameters.AddWithValue("@UserID",UserID);
     cmd.ExceuteNonQuery();
   } 

}

带SP

Using (SqlConnection Sqlconn=new  
SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString))
{

  Sqlconn.open();

  Using (Sqlcommand cmd=new Sqlcommand())
  {
    cmd.CommandType=CommandType.StoredProcedure;
    cmd.CommandText="Data_Ins_Upd_Del";
    cmd.Parameters.AddWithValue("@UserID",UserID);
    cmd.ExceuteNonQuery();
    cmd.Parameters.Clear();
  } 

}

并在SQL ServerCreate an SP like

Create Procedure Data_Ins_Upd_Del
(
@UserID Varchar(50)
)
AS
Begin
Begin Try
Declare @CONTEXT_INFO Varbinary(max)

SET @CONTEXT_INFO =cast('UserID='+CONVERT(varchar(10),@UserID)
+REPLICATE(' ',128) as varbinary(128))

SET CONTEXT_INFO @CONTEXT_INFO

/* Do Insert / Update / Delete that will fire the trigger */

SET CONTEXT_INFO 0x0 

End Try
Begin Catch
    Declare @Errmsg Varchar(max),@ErrSeverity int
    Set @Errmsg=ERROR_MESSAGE()
    Set @ErrSeverity=ERROR_SEVERITY()
    Raiserror(@Errmsg,@ErrSeverity,1)
End Catch
End

并在触发器中添加以下行

ALTER TRIGGER [dbo].[TR_lOCATION_AUDIT] 
ON [dbo].[lOCATION] FOR UPDATE,INSERT,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),
  @UserID  varchar(50), //New Line
  @sCONTEXT_INFO  varchar(128)//New Line

//Start of new Line in Trigger
SELECT @sCONTEXT_INFO=CAST(CONTEXT_INFO() AS VARCHAR) FROM master.dbo.SYSPROCESSES WHERE SPID=@@SPID 

IF Substring(RTRIM(@sCONTEXT_INFO),LEN(RTRIM(@sCONTEXT_INFO))-15,8)  like '%UserID%'
BEGIN 

    SET @UserID=RIGHT(RTRIM(@sCONTEXT_INFO),LEN(RTRIM(@sCONTEXT_INFO))-7) //New Line

END
ELSE 
BEGIN

    RAISERROR('@UserID was not specified',16,1) 
    ROLLBACK TRAN
    RETURN
END 
//End of new Line in Trigger

--You will need to change @TableName to match the table to be audited. 
-- Here we made GUESTS for your example.
SELECT @TableName = 'lOCATION'

-- date and user
SELECT @UserName = @UserID,
       @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 + ''''
       + ',''' + @UserID + ''''
       + ' 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

注意：我输入的Substring长度是根据我的测试数据改变它根据你的参数长度

编辑 SP

ALTER Procedure [dbo].[Data_Ins_Upd_Del]
(
@UserID Varchar(50),
@state varchar(100),
@dist varchar(100)
)
AS
Begin
Begin Try
Declare @CONTEXT_INFO Varbinary(max)

SET @CONTEXT_INFO =cast('UserID='+CONVERT(varchar(10),@UserID)
+REPLICATE(' ',128) as varbinary(128))

SET CONTEXT_INFO @CONTEXT_INFO

/* Do Insert / Update / Delete that will fire the trigger */
insert into State_tbl(StateName,District)values(@State,@dist)

SET CONTEXT_INFO 0x0 

End Try
Begin Catch
    Declare @Errmsg Varchar(max),@ErrSeverity int
    Set @Errmsg=ERROR_MESSAGE()
    Set @ErrSeverity=ERROR_SEVERITY()
    Raiserror(@Errmsg,@ErrSeverity,1)
End Catch
End

下面是我用来测试场景的查询和触发器

Declare @UserID varchar(50)='Usr-120',
 @CONTEXT_INFO Varbinary(max)

SET @CONTEXT_INFO =cast('UserID='+CONVERT(varchar(10),@UserID)
+REPLICATE(' ',128) as varbinary(128))

SET CONTEXT_INFO @CONTEXT_INFO

Insert into existing(UserName) Values(@UserID)

SET CONTEXT_INFO 0x0 

扳机

Alter Trigger trgExisting  
on Existing for Insert,Update,Delete  
as  

DECLARE @UserID     varchar(50)  
       ,@sCONTEXT_INFO  varchar(128)  
SELECT @sCONTEXT_INFO=CAST(CONTEXT_INFO() AS VARCHAR) 
 FROM master.dbo.SYSPROCESSES WHERE SPID=@@SPID  


IF Substring(RTRIM(@sCONTEXT_INFO),LEN(RTRIM(@sCONTEXT_INFO))-15,8) like '%UserID%'  
BEGIN  

    SET @UserID=RIGHT(RTRIM(@sCONTEXT_INFO),LEN(RTRIM(@sCONTEXT_INFO))-7) 

END  
ELSE  
BEGIN  

    RAISERROR('@UserID was not specified',16,1)  
    ROLLBACK TRAN  
    RETURN  
END

这是我通过State_Tbl使用触发器测试您的表而得到的结果

注意：此概念仅适用于Insert而不Update适用Delete

使用的触发器

Create TRIGGER [dbo].[TR_lOCATION_AUDIT] 
ON [dbo].[State_Tbl] FOR UPDATE,INSERT,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),
  @UserID  varchar(50),
  @sCONTEXT_INFO  varchar(128)


SELECT @sCONTEXT_INFO=CAST(CONTEXT_INFO() AS VARCHAR) FROM master.dbo.SYSPROCESSES WHERE SPID=@@SPID 

IF Substring(RTRIM(@sCONTEXT_INFO),LEN(RTRIM(@sCONTEXT_INFO))-15,8)  like '%UserID%'
BEGIN 

    SET @UserID=RIGHT(RTRIM(@sCONTEXT_INFO),LEN(RTRIM(@sCONTEXT_INFO))-7)

END
ELSE 
BEGIN

    RAISERROR('@UserID was not specified',16,1) 
    ROLLBACK TRAN
    RETURN
END 


--You will need to change @TableName to match the table to be audited. 
-- Here we made GUESTS for your example.
SELECT @TableName = 'State_Tbl'

-- date and user
SELECT @UserName = @UserID,
       @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
IF  Not EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Audit]') AND type in (N'U'))
Create TABLE [dbo].[Audit]
(
  TranType Varchar(150), 
  TableName Varchar(150), 
  PK Varchar(150), 
  FieldName Varchar(150), 
  OldValue Varchar(150), 
  NewValue Varchar(150), 
  UpdateDate Varchar(150), 
  UserName Varchar(150)
)

               SELECT @sql = '
insert Audit ( TranType, 
               TableName, 
               PK, 
               FieldName, 
               OldValue, 
               NewValue, 
               UpdateDate, 
               UserName)
select ''' + @Type + ''',''' 
       + @TableName + ''',' + @PKSelect
       + ',''' + @fieldname + ''''
       + ',convert(varchar(1000),d.' + @fieldname + ')'
       + ',convert(varchar(1000),i.' + @fieldname + ')'
       + ',''' + @UpdateDate + ''''
       + ',''' + @UserID + ''''
       + ' 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