SQL并行与否的性能差异

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。

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。

SQL Server 执行时间:

CPU 时间= 0 毫秒，占用时间= 335 毫秒。

SQL Server 执行时间:

CPU 时间= 33954 毫秒，占用时间= 35315毫秒。

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。

SQL Server 执行时间:

CPU 时间= 93 毫秒，占用时间= 167毫秒

1. SELECT @bin = @bin + CASE @withDeviceID
2.                                         WHEN 0 THEN 0x
3.                                         ELSECAST (deviceid ASBINARY(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 ASBINARY(1))
10.                                         + CAST (TranscationType ASBINARY(1))
11.                                         + CAST (Station ASBINARY(1))
12.                                         + dbo.int2Bin_3byte(PReBalance)
13.                                         + dbo.int2Bin_3byte(Amount)
14.                                         + dbo.time2utcbin(TranscationTime)
15.                                         + CAST (DeviceType ASBINARY(1))
16.                                         + dbo.int2Bin(TotalIntegral)
17.                                         + dbo.short2bin(Integral)
18.                                         + dbo.int2Bin(AccountCount)
19.                                         + CAST (Account ASBINARY(1))
20.                                         + dbo.int2Bin(Balance)
21.                                         + dbo.int2bin_3byte(Price)
22.                                         + CAST (Period ASBINARY(1))
23.                                         + dbo.int2Bin(Device)
24.                                         + CAST (InOutFlag ASBINARY(1))
25.                                         + CAST (UpDownFlag ASBINARY(1))
26.                                         + dbo.short2bin(Operator)
27.                                         + CAST (CardStandard ASBINARY(1))
28.                                         + CAST (TranscationMode ASBINARY(1))
29.                                         + CAST (0 ASBINARY(1))
30.                                         + CAST(0 ASBINARY(7)) + 0x55, 0, 62,
31.                                         63)
32.                 FROM @record

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