SQLSERVR语句 in和exists哪个效率高本人测试证明 最近很多人讨论in和exists哪个效率高，今天就自己测试一下 我使用的是客户的数据库GPOSDB(已经有数据) 环境 ：SQLSERVER2005 Windows7 我的测试条件 ：两个表作连接根据VC_IC_CardNO字段，查出CT_InhouseCard
最近很多人讨论in和exists哪个效率高，今天就自己测试一下
我使用的是客户的数据库GPOSDB(已经有数据)
环境：SQLSERVER2005 Windows7
我的测试条件：两个表作连接根据VC_IC_CardNO字段，查出CT_InhouseCard表中的VC_IC_CardNO（卡号）在CT_FuelingData表中存在的记录
前提：某些人可能在SQL语句中有多个in，或者多个exists，这些情况很难测试效率的，因为大家的条件都不相同
例如下面两个SQL语句
<span>1</span> <span>SELECT</span><span> OrderNo, SiteCode, AreaCode </span><span>2</span> <span>FROM</span><span> SchedulingProgram </span><span>3</span> <span>WHERE</span> AreaCode <span>IN</span> ( <span>'</span><span>P</span><span>'</span>, <span>'</span><span>M</span><span>'</span> ) <span>AND</span> SiteCode <span>IN</span> ( <span>SELECT</span><span> SiteCode </span><span>4</span> <span>FROM</span><span> EnvBasicInfo </span><span>5</span> <span>WHERE</span> cityiD <span>=</span> <span>31</span> ) <span>AND</span> OrderNo <span>NOT</span> <span>IN</span><span> ( </span><span>6</span> <span>SELECT</span><span> OrderNo </span><span>7</span> <span>FROM</span> KK_DeliveryinfoTmp )
上面SQL语句IN里面有IN和NOT IN
<span>1</span> <span>SELECT</span><span> OrderNo, SiteCode, AreaCode </span><span>2</span> <span>FROM</span><span> SchedulingProgram </span><span>3</span> <span>WHERE</span> ( AreaCode <span>IN</span> ( <span>'</span><span>P</span><span>'</span>, <span>'</span><span>M</span><span>'</span> ) <span>AND</span> SiteCode <span>IN</span> ( <span>SELECT</span><span> SiteCode </span><span>4</span> <span>FROM</span><span> EnvBasicInfo </span><span>5</span> <span>WHERE</span> cityiD <span>=</span> <span>31</span><span> ) </span><span>6</span> ) <span>AND</span> <span>NOT</span> <span>EXISTS</span> ( <span>SELECT</span><span> OrderNo </span><span>7</span> <span>FROM</span><span> KK_DeliveryinfoTmp </span><span>8</span> <span>WHERE</span> KK_DeliveryinfoTmp.OrderNo <span>=</span> SchedulingProgram.OrderNo )
上面的SQL语句IN里面又有NOT EXISTS
这样的情况很难测试同等条件下IN语句和EXISTS语句的效率
还有一个非SARG运算符
在《SQLSERVER企业级平台管理实践》的第424页里提到：
SQLSERVER对筛选条件（search argument/SARG）的写法有一定的建议
对于不使用SARG运算符的表达式，索引是没有用的，SQLSERVER对它们很难使用比较优化的做法。非SARG运算符包括
NOT、、NOT EXISTS、NOT IN、NOT LIKE和内部函数，例如：Convert、Upper等
所以当您的表中有索引并且SQL语句包含非SARG运算符，那么当测试SQL语句的执行时间的时候肯定相差很大，
因为有些SQL语句走索引，有些SQL语句不走索引
建表脚本
注意：两个表中都有索引！！
CT_FuelingData表
<span> 1</span> <span>USE</span> <span>[</span><span>GPOSDB</span><span>]</span> <span> 2</span> <span>GO</span> <span> 3</span> <span>/*</span><span>***** 对象: Table [dbo].[CT_FuelingData] 脚本日期: 08/24/2013 11:00:34 *****</span><span>*/</span> <span> 4</span> <span>SET</span> ANSI_NULLS <span>ON</span> <span> 5</span> <span>GO</span> <span> 6</span> <span>SET</span> QUOTED_IDENTIFIER <span>ON</span> <span> 7</span> <span>GO</span> <span> 8</span> <span>SET</span> ANSI_PADDING <span>ON</span> <span> 9</span> <span>GO</span> <span>10</span> <span>CREATE</span> <span>TABLE</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_FuelingData</span><span>]</span><span>( </span><span>11</span> <span>[</span><span>RecordNO</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>IDENTITY</span>(<span>1</span>,<span>1</span>) <span>NOT</span> <span>NULL</span><span>, </span><span>12</span> <span>[</span><span>I_FD_StationNo</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NOT</span> <span>NULL</span><span>, </span><span>13</span> <span>[</span><span>VC_FD_No</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NOT</span> <span>NULL</span><span>, </span><span>14</span> <span>[</span><span>VC_FD_Cardno</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NOT</span> <span>NULL</span><span>, </span><span>15</span> <span>[</span><span>I_FD_CardStatus</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>16</span> <span>[</span><span>LI_FD_CTC</span><span>]</span> <span>[</span><span>bigint</span><span>]</span> <span>NOT</span> <span>NULL</span><span>, </span><span>17</span> <span>[</span><span>I_FD_TypeCode</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>18</span> <span>[</span><span>I_FD_PumpID</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NOT</span> <span>NULL</span><span>, </span><span>19</span> <span>[</span><span>VC_FD_OilType</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>20</span> <span>[</span><span>DE_FD_Volume</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>21</span> <span>[</span><span>DE_FD_Price</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>22</span> <span>[</span><span>DE_FD_Amount</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>23</span> <span>[</span><span>I_FD_Point</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>10</span>, <span>2</span>) <span>NULL</span><span>, </span><span>24</span> <span>[</span><span>D_FD_DateTime</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NOT</span> <span>NULL</span><span>, </span><span>25</span> <span>[</span><span>VC_FD_GroupNo</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>26</span> <span>[</span><span>D_FD_GroupDate</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NULL</span><span>, </span><span>27</span> <span>[</span><span>DE_FD_CardAmount</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>28</span> <span>[</span><span>DE_FD_VolumeTotals</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>29</span> <span>[</span><span>DE_FD_AmountTotals</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>30</span> <span>[</span><span>I_FD_ISSend</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>31</span> <span>[</span><span>VC_FD_CardMoneyauthFile</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>32</span> <span>[</span><span>D_Month</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NULL</span><span>, </span><span>33</span> <span>CONSTRAINT</span> <span>[</span><span>PK_CT_FuelingData_1</span><span>]</span> <span>PRIMARY</span> <span>KEY</span> <span>CLUSTERED</span> <span>34</span> <span>( </span><span>35</span> <span>[</span><span>VC_FD_No</span><span>]</span> <span>ASC</span> <span>36</span> )<span>WITH</span> (PAD_INDEX <span>=</span> <span>OFF</span>, STATISTICS_NORECOMPUTE <span>=</span> <span>OFF</span>, IGNORE_DUP_KEY <span>=</span> <span>OFF</span>, ALLOW_ROW_LOCKS <span>=</span> <span>ON</span>, ALLOW_PAGE_LOCKS <span>=</span> <span>ON</span>) <span>ON</span> <span>[</span><span>PRIMARY</span><span>]</span> <span>37</span> ) <span>ON</span> <span>[</span><span>PRIMARY</span><span>]</span> <span>38</span> <span>39</span> <span>GO</span> <span>40</span> <span>SET</span> ANSI_PADDING <span>OFF</span>
CT_InhouseCard表
<span> 1</span> <span>USE</span> <span>[</span><span>GPOSDB</span><span>]</span> <span> 2</span> <span>GO</span> <span> 3</span> <span>/*</span><span>***** 对象: Table [dbo].[CT_InhouseCard] 脚本日期: 08/24/2013 10:59:58 *****</span><span>*/</span> <span> 4</span> <span>SET</span> ANSI_NULLS <span>ON</span> <span> 5</span> <span>GO</span> <span> 6</span> <span>SET</span> QUOTED_IDENTIFIER <span>ON</span> <span> 7</span> <span>GO</span> <span> 8</span> <span>SET</span> ANSI_PADDING <span>ON</span> <span> 9</span> <span>GO</span> <span>10</span> <span>CREATE</span> <span>TABLE</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_InhouseCard</span><span>]</span><span>( </span><span>11</span> <span>[</span><span>RecordNO</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>IDENTITY</span>(<span>1</span>,<span>1</span>) <span>NOT</span> <span>NULL</span><span>, </span><span>12</span> <span>[</span><span>VC_IC_CardNO</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NOT</span> <span>NULL</span><span>, </span><span>13</span> <span>[</span><span>VC_IC_PhysicalNO</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>14</span> <span>[</span><span>I_IC_CardType</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>15</span> <span>[</span><span>VC_IC_UserName</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>16</span> <span>[</span><span>VC_IC_JobNO</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>17</span> <span>[</span><span>VC_IC_UserID</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>18</span> <span>[</span><span>VC_IC_Password</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>19</span> <span>[</span><span>DE_IC_CardAmount</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>20</span> <span>[</span><span>DE_IC_AppendAmount</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>21</span> <span>[</span><span>DE_IC_ConsumerAmount</span><span>]</span> <span>[</span><span>decimal</span><span>]</span>(<span>18</span>, <span>2</span>) <span>NULL</span><span>, </span><span>22</span> <span>[</span><span>I_IC_ISLost</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>23</span> <span>[</span><span>D_IC_UsedDateTime</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NULL</span><span>, </span><span>24</span> <span>[</span><span>D_IC_UselifeDateTime</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NULL</span><span>, </span><span>25</span> <span>[</span><span>I_IC_IssueStationNO</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>26</span> <span>[</span><span>VC_IC_IssuerNO</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>50</span>) <span>NULL</span><span>, </span><span>27</span> <span>[</span><span>D_IC_IssueDateTime</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NULL</span><span>, </span><span>28</span> <span>[</span><span>D_IC_LastUpdateDateTime</span><span>]</span> <span>[</span><span>datetime</span><span>]</span> <span>NULL</span><span>, </span><span>29</span> <span>[</span><span>I_IC_CardStatus</span><span>]</span> <span>[</span><span>int</span><span>]</span> <span>NULL</span><span>, </span><span>30</span> <span>[</span><span>VC_IC_Remark</span><span>]</span> <span>[</span><span>varchar</span><span>]</span>(<span>256</span>) <span>NULL</span><span>, </span><span>31</span> <span>CONSTRAINT</span> <span>[</span><span>PK_CT_InhouseCard</span><span>]</span> <span>PRIMARY</span> <span>KEY</span> <span>CLUSTERED</span> <span>32</span> <span>( </span><span>33</span> <span>[</span><span>VC_IC_CardNO</span><span>]</span> <span>ASC</span> <span>34</span> )<span>WITH</span> (PAD_INDEX <span>=</span> <span>OFF</span>, STATISTICS_NORECOMPUTE <span>=</span> <span>OFF</span>, IGNORE_DUP_KEY <span>=</span> <span>OFF</span>, ALLOW_ROW_LOCKS <span>=</span> <span>ON</span>, ALLOW_PAGE_LOCKS <span>=</span> <span>ON</span>) <span>ON</span> <span>[</span><span>PRIMARY</span><span>]</span> <span>35</span> ) <span>ON</span> <span>[</span><span>PRIMARY</span><span>]</span> <span>36</span> <span>37</span> <span>GO</span> <span>38</span> <span>SET</span> ANSI_PADDING <span>OFF</span>
测试脚本
因为这个是客户的数据库，本来里面已经有数据了，所以在测试之前先更新两个表的统计信息，以做到公正
<span>1</span> <span>USE</span> <span>[</span><span>GPOSDB</span><span>]</span> <span>2</span> <span>GO</span> <span>3</span> <span>UPDATE</span> <span>STATISTICS</span><span> CT_FuelingData </span><span>4</span> <span>UPDATE</span> <span>STATISTICS</span><span> CT_InhouseCard </span><span>5</span> <span>GO</span>
IN语句
<span> 1</span> <span>USE</span> <span>[</span><span>GPOSDB</span><span>]</span> <span> 2</span> <span>GO</span> <span> 3</span> <span>DBCC</span><span> DROPCLEANBUFFERS </span><span> 4</span> <span>GO</span> <span> 5</span> <span>DBCC</span><span> FREEPROCCACHE </span><span> 6</span> <span>GO</span> <span> 7</span> <span>SET</span> <span>STATISTICS</span> IO <span>ON</span> <span> 8</span> <span>GO</span> <span> 9</span> <span>SET</span> <span>STATISTICS</span> TIME <span>ON</span> <span>10</span> <span>GO</span> <span>11</span> <span>SET</span> <span>STATISTICS</span> PROFILE <span>ON</span> <span>12</span> <span>GO</span> <span>13</span> <span>SELECT</span> <span>*</span> <span>FROM</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_FuelingData</span><span>]</span> <span>WHERE</span> <span>[</span><span>VC_FD_Cardno</span><span>]</span> <span>IN</span> (<span>SELECT</span> <span>[</span><span>VC_IC_CardNO</span><span>]</span> <span>FROM</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_InhouseCard</span><span>]</span>)
EXISTS语句
<span> 1</span> <span>USE</span> <span>[</span><span>GPOSDB</span><span>]</span> <span> 2</span> <span>GO</span> <span> 3</span> <span>DBCC</span><span> DROPCLEANBUFFERS </span><span> 4</span> <span>GO</span> <span> 5</span> <span>DBCC</span><span> FREEPROCCACHE </span><span> 6</span> <span>GO</span> <span> 7</span> <span>SET</span> <span>STATISTICS</span> IO <span>ON</span> <span> 8</span> <span>GO</span> <span> 9</span> <span>SET</span> <span>STATISTICS</span> TIME <span>ON</span> <span>10</span> <span>GO</span> <span>11</span> <span>SET</span> <span>STATISTICS</span> PROFILE <span>ON</span> <span>12</span> <span>GO</span> <span>13</span> <span>SELECT</span> <span>*</span> <span>14</span> <span>FROM</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_FuelingData</span><span>]</span> <span>15</span> <span>WHERE</span> <span>EXISTS</span> ( <span>SELECT</span> <span>[</span><span>VC_IC_CardNO</span><span>]</span> <span>16</span> <span>FROM</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_InhouseCard</span><span>]</span> <span>17</span> <span>WHERE</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_FuelingData</span><span>]</span>.<span>[</span><span>VC_FD_Cardno</span><span>]</span> <span>=</span> <span>[</span><span>dbo</span><span>]</span>.<span>[</span><span>CT_InhouseCard</span><span>]</span>.<span>[</span><span>VC_IC_CardNO</span><span>]</span> )
测试结果
IN语句
<span> 1</span> <span>SQL Server 执行时间: </span><span> 2</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>2</span><span> 毫秒。 </span><span> 3</span> <span>SQL Server 分析和编译时间: </span><span> 4</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span> 5</span> <span> 6</span> <span>SQL Server 执行时间: </span><span> 7</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span> 8</span> <span>SQL Server 分析和编译时间: </span><span> 9</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span>10</span> <span>11</span> <span>SQL Server 执行时间: </span><span>12</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span>13</span> <span>SQL Server 分析和编译时间: </span><span>14</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span>15</span> <span>16</span> <span>SQL Server 执行时间: </span><span>17</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span>18</span> <span>SQL Server 分析和编译时间: </span><span>19</span> CPU 时间 <span>=</span> <span>31</span> 毫秒，占用时间 <span>=</span> <span>67</span><span> 毫秒。 </span><span>20</span> <span>21</span> (<span>167</span><span> 行受影响) </span><span>22</span> 表 <span>'</span><span>Worktable</span><span>'</span>。扫描计数 <span>0</span>，逻辑读取 <span>0</span> 次，物理读取 <span>0</span> 次，预读 <span>0</span> 次，lob 逻辑读取 <span>0</span> 次，lob 物理读取 <span>0</span> 次，lob 预读 <span>0</span><span> 次。 </span><span>23</span> 表 <span>'</span><span>CT_FuelingData</span><span>'</span>。扫描计数 <span>1</span>，逻辑读取 <span>31</span> 次，物理读取 <span>1</span> 次，预读 <span>64</span> 次，lob 逻辑读取 <span>0</span> 次，lob 物理读取 <span>0</span> 次，lob 预读 <span>0</span><span> 次。 </span><span>24</span> 表 <span>'</span><span>CT_InhouseCard</span><span>'</span>。扫描计数 <span>1</span>，逻辑读取 <span>2</span> 次，物理读取 <span>1</span> 次，预读 <span>0</span> 次，lob 逻辑读取 <span>0</span> 次，lob 物理读取 <span>0</span> 次，lob 预读 <span>0</span><span> 次。 </span><span>25</span> <span>26</span> (<span>4</span><span> 行受影响) </span><span>27</span> <span>28</span> <span>SQL Server 执行时间: </span><span>29</span> CPU 时间 <span>=</span> <span>16</span> 毫秒，占用时间 <span>=</span> <span>192</span> 毫秒。
EXISTS语句
<span> 1</span> <span>SQL Server 分析和编译时间: </span><span> 2</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span> 3</span> <span> 4</span> <span>SQL Server 执行时间: </span><span> 5</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>0</span><span> 毫秒。 </span><span> 6</span> <span>SQL Server 分析和编译时间: </span><span> 7</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>34</span><span> 毫秒。 </span><span> 8</span> <span> 9</span> (<span>167</span><span> 行受影响) </span><span>10</span> 表 <span>'</span><span>Worktable</span><span>'</span>。扫描计数 <span>0</span>，逻辑读取 <span>0</span> 次，物理读取 <span>0</span> 次，预读 <span>0</span> 次，lob 逻辑读取 <span>0</span> 次，lob 物理读取 <span>0</span> 次，lob 预读 <span>0</span><span> 次。 </span><span>11</span> 表 <span>'</span><span>CT_FuelingData</span><span>'</span>。扫描计数 <span>1</span>，逻辑读取 <span>31</span> 次，物理读取 <span>1</span> 次，预读 <span>64</span> 次，lob 逻辑读取 <span>0</span> 次，lob 物理读取 <span>0</span> 次，lob 预读 <span>0</span><span> 次。 </span><span>12</span> 表 <span>'</span><span>CT_InhouseCard</span><span>'</span>。扫描计数 <span>1</span>，逻辑读取 <span>2</span> 次，物理读取 <span>1</span> 次，预读 <span>0</span> 次，lob 逻辑读取 <span>0</span> 次，lob 物理读取 <span>0</span> 次，lob 预读 <span>0</span><span> 次。 </span><span>13</span> <span>14</span> (<span>4</span><span> 行受影响) </span><span>15</span> <span>16</span> <span>SQL Server 执行时间: </span><span>17</span> CPU 时间 <span>=</span> <span>0</span> 毫秒，占用时间 <span>=</span> <span>163</span> 毫秒。
大家可以看到除了执行时间有一点差别，IO是一样的
因为数据量比较大，所以两个查询都用到了Worktable（中间表）来存储中间结果
IN语句的执行计划
EXISTS语句的执行计划
从执行计划可以看到两个SQL语句的开销都是一样的，而且大家都使用了右半连接（Right Semi Join）
至于什么是半连接（Semi-join）大家可以看一下这篇文章：SQL Join的一些总结
总结
从上面实际的执行来比较,，IN语句和EXISTS语句基本上都是一样的效率
如有不对的地方，欢迎大家来拍砖o(∩_∩)o
