Sql server 2012 SSIS SSQL任务错误

我试图在SSIS中使用SQL任务更新表，但遇到错误：无法绑定多部分标识符“a.SourceSystemKey”

Update BMR_STAGE.dbo.STG_AL_VSAccountStatuses
set a.SourceSystemKey = b.SourceSystemKey
,a.SourceSystem = b.SourceSystem
,a.NLCompany = b.NLCompany
,a.AccountStatus = b.AccountStatus
,a.Description = b.Description
,a.InsertAuditKey = b.InsertAuditKey
,a.UpdateAuditKey = b.UpdateAuditKey
,a.ChangeDate = b.ChangeDate
from  BMR_STAGE.dbo.STG_AL_VSAccountStatuses a, BMR_STAGE.dbo.TMP_STG_AL_VSAccountStatuses b
where a.ID =b.ID

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该错误表示没有名为a.SourceSystemKey的字段，或者在该范围内无法识别别名a。尝试使用显式联接语法

Update a 
set  
a.SourceSystemKey = b.SourceSystemKey
,a.SourceSystem = b.SourceSystem
,a.NLCompany = b.NLCompany
,a.AccountStatus = b.AccountStatus
,a.Description = b.Description
,a.InsertAuditKey = b.InsertAuditKey
,a.UpdateAuditKey = b.UpdateAuditKey
,a.ChangeDate = b.ChangeDate
from BMR_STAGE.dbo.STG_AL_VSAccountStatuses a inner join 
BMR_STAGE.dbo.TMP_STG_AL_VSAccountStatuses b on a.ID = b.ID