UPDATE a
SET    a.ProductSku = b.ProductSku
FROM   RB_Shopee_Listing_Parent a (nolock)
       INNER JOIN RB_Shopee_Listing_Parent b (nolock)
               ON a.CustomerId = b.CustomerID
                  AND a.MappingGlobalItemId = b.ShopeeId
WHERE  a.CustomerId = 1
       AND a.ListingVersion = 2
       AND ( a.ProductSku = ''
              OR a.ProductSku IS NULL )
       AND a.MappingGlobalItemId >0
AND b.ListingVersion != 2
AND (a.sku<>'' OR a.Sku IS NOT NULL)

分析一下重复调用的原因。