当源表中没有记录时，为什么sql server会对连接进行扫描

下面查询的思路是使用 CTE 获取 [Archive].[tia_tia_object] 中所有满足过滤器的行的主键。

CTE 内查询的执行时间为 0 秒。

第二部分应该在其他表上进行连接，以更多地过滤数据，但前提是 CTE 中返回了任何行。这是我可以让 SQL 服务器使用正确索引的唯一方法。

当 CTE 返回 0 行时，为什么要花时间（参见执行计划）查看 TIA_TIA_AGREEMENT_LINE 和 TIA_TIA_OBJECT？

WITH cte_vehicle 
     AS (SELECT O.[Seq_no], 
                O.Object_No 
         FROM   [Archive].[tia_tia_object] O 
         WHERE  O.RECORD_TIMESTAMP > 
            (SELECT LastLoadTimeStamp FROM staging.Ufngetlastloadtimestamp('Staging.CoveredObject')) 
            AND O.[Meta_iscurrent] = 1 
            AND O.OBJECT_TYPE IN ( 'BIO01', 'CAO01', 'DKV', 'GFO01', 
                                   'KMA', 'KNO01', 'MCO01', 'VEO01', 
                                   'SVO01', 'AUO01' )) 
SELECT O.[Seq_no]                      AS [Bkey_CoveredObject], 
       Cast(O.[Agr_Line_No] AS BIGINT) AS [Agr_Line_No], 
       O.[Cover_Start_Date]            AS [CoverageFrom], 
       O.[Cover_End_Date]              AS [CoverageTo], 
       O.[Timestamp]                   AS [TIMESTAMP], 
       O.[Record_Timestamp]            AS [RECORD_TIMESTAMP], 
       O.[Newest]                      AS [Newest], 
       O.LOCATION_ID                   AS LocationNo, 
       O.[Cust_no], 
       O.[N01] 
FROM   cte_vehicle AS T 
       INNER JOIN [Archive].[tia_tia_object] O 
               ON t.Object_No = O.Object_No 
                  AND t.Seq_No = O.Seq_No 
       INNER JOIN [Archive].[tia_tia_agreement_line] AL 
               ON O.Agr_line_no = AL.Agr_line_no 
       INNER JOIN [Archive].[tia_tia_policy] P
                ON AL.Policy_no = P.Policy_no 
WHERE  P.[Transaction_type] <> 'D' 

执行计划：