比较两种代码，核心代码相同，其中一个使用变量保存查询出的结果，另一个直接输出。使用同一变量时，强迫SQL放弃了并行，使用了循环。

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测试结果

表‘#1699586C‘。扫描计数1，逻辑读取186 次，物理读取0 次，预读0 次，lob 逻辑读取0 次，lob 物理读取0 次，lob 预读0 次。

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SQL Server 执行时间:

CPU 时间= 0 毫秒，占用时间= 335 毫秒。

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SQL Server 执行时间:

CPU 时间= 33954 毫秒，占用时间= 35315 毫秒。

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表‘#1699586C‘。扫描计数1，逻辑读取186 次，物理读取0 次，预读0 次，lob 逻辑读取0 次，lob 物理读取0 次，lob 预读0 次。

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SQL Server 执行时间:

CPU 时间= 93 毫秒，占用时间= 167 毫秒

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1. SELECT @bin = @bin + CASE @withDeviceID
2. ????????????????????????????????????????WHEN 0 THEN 0x
3. ????????????????????????????????????????ELSE CAST (deviceid AS BINARY(16))
4. ??????????????????????????????????????END
5. ????????????????????????+ dbo.updatesum(dbo.long2Bin_4byte(CardSerialNo)
6. ????????????????????????????????????????+ dbo.long2Bin_4byte(Tac)
7. ????????????????????????????????????????+ dbo.long2Bin(CardSeq)
8. ????????????????????????????????????????+ dbo.int2Bin(HardwareNo)
9. ????????????????????????????????????????+ CAST (CardType AS BINARY(1))
10. ????????????????????????????????????????+ CAST (TranscationType AS BINARY(1))
11. ????????????????????????????????????????+ CAST (Station AS BINARY(1))
12. ????????????????????????????????????????+ dbo.int2Bin_3byte(PreBalance)
13. ????????????????????????????????????????+ dbo.int2Bin_3byte(Amount)
14. ????????????????????????????????????????+ dbo.time2utcbin(TranscationTime)
15. ????????????????????????????????????????+ CAST (DeviceType AS BINARY(1))
16. ????????????????????????????????????????+ dbo.int2Bin(TotalIntegral)
17. ????????????????????????????????????????+ dbo.short2bin(Integral)
18. ????????????????????????????????????????+ dbo.int2Bin(AccountCount)
19. ????????????????????????????????????????+ CAST (Account AS BINARY(1))
20. ????????????????????????????????????????+ dbo.int2Bin(Balance)
21. ????????????????????????????????????????+ dbo.int2bin_3byte(Price)
22. ????????????????????????????????????????+ CAST (Period AS BINARY(1))
23. ????????????????????????????????????????+ dbo.int2Bin(Device)
24. ????????????????????????????????????????+ CAST (InOutFlag AS BINARY(1))
25. ????????????????????????????????????????+ CAST (UpDownFlag AS BINARY(1))
26. ????????????????????????????????????????+ dbo.short2bin(Operator)
27. ????????????????????????????????????????+ CAST (CardStandard AS BINARY(1))
28. ????????????????????????????????????????+ CAST (TranscationMode AS BINARY(1))
29. ????????????????????????????????????????+ CAST (0 AS BINARY(1))
30. ????????????????????????????????????????+ CAST(0 AS BINARY(7)) + 0x55, 0, 62,
31. ????????????????????????????????????????63)
32. ????????????????FROM @record

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1. SELECT CASE 1
2. ??????????WHEN 0 THEN 0x
3. ??????????ELSE CAST (deviceid AS BINARY(16))
4. ????????END + dbo.updatesum(dbo.long2Bin_4byte(CardSerialNo)
5. ????????????????????????????+ dbo.long2Bin_4byte(Tac) + dbo.long2Bin(CardSeq)
6. ????????????????????????????+ dbo.int2Bin(HardwareNo)
7. ????????????????????????????+ CAST (CardType AS BINARY(1))
8. ????????????????????????????+ CAST (TranscationType AS BINARY(1))
9. ????????????????????????????+ CAST (Station AS BINARY(1))
10. ????????????????????????????+ dbo.int2Bin_3byte(PreBalance)
11. ????????????????????????????+ dbo.int2Bin_3byte(Amount)
12. ????????????????????????????+ dbo.time2utcbin(TranscationTime)
13. ????????????????????????????+ CAST (DeviceType AS BINARY(1))
14. ????????????????????????????+ dbo.int2Bin(TotalIntegral)
15. ????????????????????????????+ dbo.short2bin(Integral)
16. ????????????????????????????+ dbo.int2Bin(AccountCount)
17. ????????????????????????????+ CAST (Account AS BINARY(1))
18. ????????????????????????????+ dbo.int2Bin(Balance) + dbo.int2bin_3byte(Price)
19. ????????????????????????????+ CAST (Period AS BINARY(1)) + dbo.int2Bin(Device)
20. ????????????????????????????+ CAST (InOutFlag AS BINARY(1))
21. ????????????????????????????+ CAST (UpDownFlag AS BINARY(1))
22. ????????????????????????????+ dbo.short2bin(Operator)
23. ????????????????????????????+ CAST (CardStandard AS BINARY(1))
24. ????????????????????????????+ CAST (TranscationMode AS BINARY(1))
25. ????????????????????????????+ CAST (0 AS BINARY(1)) + CAST(0 AS BINARY(7))
26. ????????????????????????????+ 0x55, 0, 62, 63)
27. FROM @record

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SQL并行与否的性能差异