Dynamic SQL delete query problem

Hi all--Given a query that returns ~557K rows on SQL Server 2005 SP1:

SELECT distinct(a.[Import_Date]),b.[Import_Date],
a.[OS_USERNAME],b.[OS_USERNAME],a.[USERNAME],b.[USERNAME],
a.[TIMESTAMP],b.[TIMESTAMP]
FROM [DBA_AUDIT_SESSION] a, [DBA_AUDIT_SESSION] b
where a.[OS_USERNAME]=b.[OS_USERNAME]
and a.[USERNAME]=b.[USERNAME]
and a.[TIMESTAMP]=b.[TIMESTAMP]
and a.[Import_Date]<b.[Import_Date]

On a table that has the following definition:

TABLE [dbo].[DBA_AUDIT_SESSION](
[Import_Date] [datetime] NULL,
[INSTANCE_NAME] [varchar](16) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[HOST_NAME] [varchar](64) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[OS_USERNAME] [varchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[USERNAME] [varchar](30) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[USERHOST] [varchar](128) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[TERMINAL] [varchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[TIMESTAMP] [datetime] NULL,
[ACTION_NAME] [varchar](27) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[LOGOFF_TIME] [datetime] NULL,
[LOGOFF_LREAD] [float] NULL,
[LOGOFF_PREAD] [float] NULL,
[LOGOFF_LWRITE] [float] NULL,
[LOGOFF_DLOCK] [varchar](40) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[SESSIONID] [float] NULL,
[RETURNCODE] [float] NULL,
[CLIENT_ID] [varchar](64) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[SESSION_CPU] [float] NULL

I would like to delete duplicate data from this table and keep only the data with the latest Import_Date. I came up with the following delete statement:

delete FROM [DBA_AUDIT_SESSION]
FROM [DBA_AUDIT_SESSION] a,
inner join [DBA_AUDIT_SESSION] b
on a.[TIMESTAMP]=b.[TIMESTAMP]
where a.[Import_Date]<b.[Import_Date];

The command parses successfully, but I get the following runtime error:
'Table DBA_AUDIT_SESSION is ambiguous.'

Does anyone have suggestions on how to fix this delete statement?

Use the TSQL update/delete statement syntax sparingly. The TSQL specific syntax can produce unexpected results if used incorrectly or performance problems also. You can use the standard DELETE statement syntax like:

-- assumes that import_date is unique per timestamp

delete [DBA_AUDIT_SESSION]

where Import_Date < (select max(a.Import_Date) from [DBA_AUDIT_SESSION] as a

where a.TimeStamp = [DBA_AUDIT_SESSION].TimeStamp)

|||This seems to do the trick, and meets all the criteria for cleanup needed. Thanks!