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집데이터 베이스MySQL 튜토리얼SQLSERVER用无中生有的思想来替代游标

SQLSERVER用无中生有的思想来替代游标

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Jun 07, 2016 pm 03:21 PM
sqlserver대리자커서

SQLSERVER用 无中生有 的 思想 来 替代 游标 昨天在MSDN论坛看到一个帖子，帖子中LZ需要根据某列的值把其他列的值插入到额外列 帖子地址： http://social.technet.microsoft.com/Forums/zh-CN/3eac78ca-d071-4c00-afa0-ef48c8501745/sql-statementcolumn-nam

SQLSERVER用无中生有的思想来替代游标

昨天在MSDN论坛看到一个帖子，帖子中LZ需要根据某列的值把其他列的值插入到额外列

帖子地址：http://social.technet.microsoft.com/Forums/zh-CN/3eac78ca-d071-4c00-afa0-ef48c8501745/sql-statementcolumn-namecolumnsql-

建表脚本：

SQLSERVER用无中生有的思想来替代游标SQLSERVER用无中生有的思想来替代游标 

<span> 1</span> <span>USE</span><span> tempdb
</span><span> 2</span> <span>GO</span>
<span> 3</span> 
<span> 4</span> <span>--</span><span>建表</span>
<span> 5</span> <span>CREATE</span> <span>TABLE</span><span> t1
</span><span> 6</span> <span>(
</span><span> 7</span>   client <span>VARCHAR</span>(<span>10</span><span>) ,
</span><span> 8</span>   pay_level <span>INT</span><span> ,
</span><span> 9</span>   pay_lv_1 <span>INT</span><span> ,
</span><span>10</span>   pay_lv_2 <span>INT</span><span> ,
</span><span>11</span>   pay_lv_3 <span>INT</span><span> ,
</span><span>12</span>   pay_lv_4 <span>INT</span><span> ,
</span><span>13</span>   pay_lv_5 <span>INT</span><span> ,
</span><span>14</span>   pay_lv_6 <span>INT</span><span> ,
</span><span>15</span>   pay_lv_7 <span>INT</span><span> ,
</span><span>16</span>   pay_lv_8 <span>INT</span><span> ,
</span><span>17</span>   pay_lv_9 <span>INT</span><span> ,
</span><span>18</span>   pay_lv_10 <span>INT</span><span> ,
</span><span>19</span>   pay_lv_11 <span>INT</span><span> ,
</span><span>20</span>   pay_lv_12 <span>INT</span><span> ,
</span><span>21</span>   pay_lv_13 <span>INT</span><span> ,
</span><span>22</span>   pay_lv_14 <span>INT</span><span> ,
</span><span>23</span>   pay_lv_15 <span>INT</span><span> ,
</span><span>24</span>   pay_lv_16 <span>INT</span><span> ,
</span><span>25</span>   pay_lv_17 <span>INT</span><span> ,
</span><span>26</span>   pay_lv_18 <span>INT</span><span> ,
</span><span>27</span>   pay_lv_19 <span>INT</span><span> ,
</span><span>28</span>   pay_lv_20 <span>INT</span><span> ,
</span><span>29</span>   pay_lv_21 <span>INT</span><span> ,
</span><span>30</span>   pay_lv_22 <span>INT</span><span> ,
</span><span>31</span>   pay_lv_23 <span>INT</span><span> ,
</span><span>32</span>   pay_lv_24 <span>INT</span><span> ,
</span><span>33</span>   pay_lv_25 <span>INT</span><span>,
</span><span>34</span> <span>);
</span><span>35</span> 
<span>36</span> 
<span>37</span> <span>--</span><span>插入测试数据</span>
<span>38</span> <span>DECLARE</span> <span>@i</span> <span>INT</span>
<span>39</span> <span>SET</span> <span>@i</span> <span>=</span> <span>1</span>
<span>40</span> <span>WHILE</span> <span>@i</span> <span> <span>8</span> 
<span>41</span>     <span>BEGIN</span>
<span>42</span>         <span>INSERT</span>  <span>INTO</span><span> t1 ( client, pay_level, pay_lv_1, pay_lv_2, pay_lv_3,
</span><span>43</span> <span>                           pay_lv_4, pay_lv_5, pay_lv_6, pay_lv_7, pay_lv_8,
</span><span>44</span> <span>                           pay_lv_9, pay_lv_10, pay_lv_11, pay_lv_12,
</span><span>45</span> <span>                           pay_lv_13, pay_lv_14, pay_lv_15, pay_lv_16,
</span><span>46</span> <span>                           pay_lv_17, pay_lv_18, pay_lv_19, pay_lv_20,
</span><span>47</span> <span>                           pay_lv_21, pay_lv_22, pay_lv_23, pay_lv_24,
</span><span>48</span> <span>                           pay_lv_25 )
</span><span>49</span>                 <span>SELECT</span>  <span>'</span><span>client</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@i</span> <span>AS</span> <span>VARCHAR</span>(<span>10</span><span>)),
</span><span>50</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>51</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>52</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>53</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>54</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>55</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>56</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>57</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>58</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>59</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>60</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>61</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span>62</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>()
</span><span>63</span>           <span>SET</span> <span>@i</span><span>=</span><span>@i</span><span>+</span><span>1</span>
<span>64</span> 
<span>65</span>     <span>END</span>
<span>66</span> 
<span>67</span> <span>SELECT</span> <span>*</span> <span>FROM</span><span> t1
</span><span>68</span> <span>GO</span></span>
View Code

SQLSERVER用无中生有的思想来替代游标

图1

LZ说原表就是类似上面那样，实际表中pay_lv_会有很多列至少100列，我这里为了测试只建了25个pay_lv_列

而LZ希望select出来的结果是下图那样

 SQLSERVER用无中生有的思想来替代游标

图2

client列和pay_level列不变，增加一个pay_cost列

pay_cost列根据pay_level列的值去取pay_lv_列的值，或者我用下面的图片会更加明白

 SQLSERVER用无中生有的思想来替代游标

图3

例如第6行，pay_level的值是6，那么就去pay_lv_6这一列的值（值是20）把他放到pay_cost列里

其他也是一样，第二行pay_level的值是10，那就去pay_lv_10这一列的值（值是17）把他放到pay_cost列里

如此类推

要select出图2的结果，有下面几种方法

1、case when

2、UNPIVOT函数

3、游标

我这里再建另外一个表，这个表跟原表是一样的，只是数据没有那么多，pay_lv_列数只有3列

SQLSERVER用无中生有的思想来替代游标SQLSERVER用无中生有的思想来替代游标 

<span> 1</span> <span>USE</span><span> tempdb
</span><span> 2</span> <span>GO</span>
<span> 3</span> 
<span> 4</span> 
<span> 5</span> <span>CREATE</span> <span>TABLE</span><span> #t
</span><span> 6</span> <span>(
</span><span> 7</span>   client <span>VARCHAR</span>(<span>10</span><span>) ,
</span><span> 8</span>   pay_level <span>INT</span><span> ,
</span><span> 9</span>   pay_lv_1 <span>INT</span><span> ,
</span><span>10</span>   pay_lv_2 <span>INT</span><span> ,
</span><span>11</span>   pay_lv_3 <span>INT</span>
<span>12</span> <span>);
</span><span>13</span> 
<span>14</span> <span>INSERT</span> <span>INTO</span><span> #t ( client ,
</span><span>15</span> <span>          pay_level ,
</span><span>16</span> <span>          pay_lv_1 ,
</span><span>17</span> <span>          pay_lv_2 ,
</span><span>18</span> <span>          pay_lv_3
</span><span>19</span> <span>        )
</span><span>20</span> <span>VALUES</span>  ( <span>'</span><span>client1</span><span>'</span> , <span>--</span><span> client - varchar(10)</span>
<span>21</span>           <span>1</span>, <span>--</span><span> pay_level - int</span>
<span>22</span>           <span>10</span> , <span>--</span><span> pay_lv_1 - int</span>
<span>23</span>           <span>12</span> , <span>--</span><span> pay_lv_2 - int</span>
<span>24</span>           <span>14</span>  <span>--</span><span> pay_lv_3 - int</span>
<span>25</span> <span>        )
</span><span>26</span> 
<span>27</span> 
<span>28</span> <span>INSERT</span> <span>INTO</span><span> #t ( client ,
</span><span>29</span> <span>          pay_level ,
</span><span>30</span> <span>          pay_lv_1 ,
</span><span>31</span> <span>          pay_lv_2 ,
</span><span>32</span> <span>          pay_lv_3
</span><span>33</span> <span>        )
</span><span>34</span> <span>VALUES</span>  ( <span>'</span><span>client2</span><span>'</span> , <span>--</span><span> client - varchar(10)</span>
<span>35</span>           <span>3</span>, <span>--</span><span> pay_level - int</span>
<span>36</span>           <span>21</span> , <span>--</span><span> pay_lv_1 - int</span>
<span>37</span>           <span>22</span> , <span>--</span><span> pay_lv_2 - int</span>
<span>38</span>           <span>23</span>  <span>--</span><span> pay_lv_3 - int</span>
<span>39</span> <span>        )
</span><span>40</span> 
<span>41</span> <span>INSERT</span> <span>INTO</span><span> #t ( client ,
</span><span>42</span> <span>          pay_level ,
</span><span>43</span> <span>          pay_lv_1 ,
</span><span>44</span> <span>          pay_lv_2 ,
</span><span>45</span> <span>          pay_lv_3
</span><span>46</span> <span>        )
</span><span>47</span> <span>VALUES</span>  ( <span>'</span><span>client3</span><span>'</span> , <span>--</span><span> client - varchar(10)</span>
<span>48</span>           <span>2</span>, <span>--</span><span> pay_level - int</span>
<span>49</span>           <span>30</span> , <span>--</span><span> pay_lv_1 - int</span>
<span>50</span>           <span>32</span> , <span>--</span><span> pay_lv_2 - int</span>
<span>51</span>           <span>33</span>  <span>--</span><span> pay_lv_3 - int</span>
<span>52</span> <span>        )
</span><span>53</span> 
<span>54</span> <span>SELECT</span> <span>*</span> <span>FROM</span> #t
View Code

（1）case when

<span>1</span> <span>SELECT</span>  client,<span>[</span><span>pay_level</span><span>]</span>,( <span>CASE</span><span> pay_level
</span><span>2</span>                   <span>WHEN</span> <span>1</span> <span>THEN</span><span> pay_lv_1
</span><span>3</span>                   <span>WHEN</span> <span>2</span> <span>THEN</span><span> pay_lv_2
</span><span>4</span>                   <span>WHEN</span> <span>3</span> <span>THEN</span><span> pay_lv_3
</span><span>5</span>                   <span>ELSE</span> <span>0</span>
<span>6</span>                 <span>END</span>) <span>AS</span> <span>'</span><span>pay_cost</span><span>'</span>
<span>7</span> <span>FROM</span>    #t;

SQLSERVER用无中生有的思想来替代游标

图4

（2）UNPIVOT函数

<span> 1</span> <span>SELECT</span>  <span>*</span> <span>INTO</span><span> #tt
</span><span> 2</span> <span>FROM</span>    ( <span>SELECT</span>    <span>*</span>
<span> 3</span>           <span>FROM</span><span>      #t
</span><span> 4</span> <span>        ) p UNPIVOT
</span><span> 5</span>    ( pay_cost <span>FOR</span> pay_lv <span>IN</span> ( pay_lv_1, pay_lv_2, pay_lv_3 ) )<span>AS</span><span> unpvt
</span><span> 6</span> <span>WHERE</span>   <span>CAST</span>(<span>RIGHT</span>(pay_lv, <span>1</span>) <span>AS</span> <span>INT</span>) <span>=</span><span> pay_level
</span><span> 7</span> 
<span> 8</span> <span>SELECT</span> <span>[</span><span>client</span><span>]</span>,<span>[</span><span>pay_level</span><span>]</span>,<span>[</span><span>pay_cost</span><span>]</span> <span>FROM</span> <span>[</span><span>#tt</span><span>]</span>
<span> 9</span> 
<span>10</span> <span>DROP</span> <span>TABLE</span> <span>[</span><span>#tt</span><span>]</span>

SQLSERVER用无中生有的思想来替代游标

图5

上面两个方法：CASE WHEN和UNPIVOT函数可以用拼接SQL的方法来做，不过由于本人功力不够，写不出来

（3）游标

 我不喜欢使用游标，主要有两个原因

1、每次用的时候，要打开笔记本看语法

2、占用资源

 我使用了下面的sql语句来解决LZ的问题

SQLSERVER用无中生有的思想来替代游标SQLSERVER用无中生有的思想来替代游标 

<span> 1</span> <span>IF</span> <span>object_id</span>(<span>'</span><span>#ttt</span><span>'</span>) <span>IS</span> <span>NOT</span> <span>NULL</span>
<span> 2</span> <span>DROP</span> <span>TABLE</span><span> #ttt
</span><span> 3</span> <span>IF</span> <span>object_id</span>(<span>'</span><span>#temptb</span><span>'</span>) <span>IS</span> <span>NOT</span> <span>NULL</span>
<span> 4</span> <span>DROP</span> <span>TABLE</span><span> #temptb
</span><span> 5</span> 
<span> 6</span> <span>DECLARE</span> <span>@i</span> <span>INT</span>
<span> 7</span>   <span>--</span><span>用于循环的</span>
<span> 8</span> <span>SET</span> <span>@i</span> <span>=</span> <span>1</span>
<span> 9</span> <span>DECLARE</span> <span>@pay_level</span> <span>INT</span>
<span>10</span>   <span>--</span><span>保存pay_level字段的值</span>
<span>11</span> <span>DECLARE</span> <span>@COUNT</span> <span>INT</span>
<span>12</span>    <span>--</span><span>保存#t1表的总行数值</span>
<span>13</span> <span>DECLARE</span> <span>@pay_lv</span> <span>INT</span>
<span>14</span>   <span>--</span><span>用于保存pay_lv的值</span>
<span>15</span> <span>DECLARE</span> <span>@sql</span> <span>NVARCHAR</span>(<span>2000</span><span>)
</span><span>16</span> 
<span>17</span> <span>CREATE</span> <span>TABLE</span> #ttt (ID <span>INT</span> <span>IDENTITY</span>(<span>1</span>,<span>1</span>), pay_cost <span>INT</span><span> )
</span><span>18</span> 
<span>19</span> <span>SELECT</span>  <span>IDENTITY</span>( <span>INT</span>,<span>1</span>,<span>1</span> ) <span>AS</span> ID, <span>*</span> <span>INTO</span>    #temptb <span>FROM</span><span>  t1
</span><span>20</span> 
<span>21</span> 
<span>22</span> <span>--</span><span>获取#t1表的总行数</span>
<span>23</span> <span>SELECT</span>  <span>@COUNT</span> <span>=</span> <span>COUNT</span>(<span>*</span>) <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span>
<span>24</span> <span>WHILE</span> <span>@i</span> <span> <span>@COUNT</span> 
<span>25</span>     <span>BEGIN</span>
<span>26</span>         <span>SELECT</span>  <span>@pay_level</span> <span>=</span> <span>[</span><span>pay_level</span><span>]</span> <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span> <span>WHERE</span>   id <span>=</span> <span>@i</span>
<span>27</span>     <span>--</span><span>判断列名是否存在，不存在就插入0</span>
<span>28</span>         <span>IF</span> <span>'</span><span>pay_lv_</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@pay_level</span> <span>AS</span> <span>VARCHAR</span>(<span>200</span>)) <span>IN</span> ( <span>SELECT</span>   NAME <span>FROM</span>     SYS.<span>[</span><span>syscolumns</span><span>]</span><span> ) 
</span><span>29</span>             <span>BEGIN</span>
<span>30</span>                 <span>--</span><span>用拼接sql的方法来获得pay_lv列对应的值，然后插入到#ttt表</span>
<span>31</span>                 <span>SET</span> <span>@sql</span> <span>=</span> N<span>'</span><span>select </span><span>'</span> <span>+</span> <span>'</span><span> @pay_lv=pay_lv_</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@pay_level</span> <span>AS</span> <span>NVARCHAR</span>(<span>200</span>)) <span>+</span> <span>'</span><span> from #temptb where id=</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@i</span> <span>AS</span> <span>NVARCHAR</span>(<span>20</span><span>))
</span><span>32</span>                 <span>EXEC</span> sp_executesql <span>@sql</span>, N<span>'</span><span>@pay_lv   int   output </span><span>'</span>, <span>@pay_lv</span><span> OUTPUT
</span><span>33</span>                 <span>INSERT</span>  <span>INTO</span> #ttt <span>VALUES</span>  (<span>@pay_lv</span><span>)
</span><span>34</span>             <span>END</span>
<span>35</span>         <span>ELSE</span> 
<span>36</span>             <span>BEGIN</span>
<span>37</span>                 <span>INSERT</span>  <span>INTO</span> #ttt <span>VALUES</span>(<span>0</span><span>)
</span><span>38</span>             <span>END</span>
<span>39</span>         <span>SET</span> <span>@i</span> <span>=</span> <span>@i</span> <span>+</span> <span>1</span>
<span>40</span>     <span>END</span>
<span>41</span> 
<span>42</span> 
<span>43</span> 
<span>44</span> <span>SELECT</span>  A.<span>[</span><span>client</span><span>]</span>, A.<span>[</span><span>pay_level</span><span>]</span>, B.<span>[</span><span>pay_cost</span><span>]</span>
<span>45</span> <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span> <span>AS</span><span> A
</span><span>46</span> <span>INNER</span> <span>JOIN</span> <span>[</span><span>#ttt</span><span>]</span> <span>AS</span> B <span>ON</span> A.<span>[</span><span>ID</span><span>]</span> <span>=</span> B.<span>[</span><span>ID</span><span>]</span>
<span>47</span> <span>ORDER</span> <span>BY</span> A.<span>[</span><span>ID</span><span>]</span> <span>ASC</span>
<span>48</span> 
<span>49</span> <span>DROP</span> <span>TABLE</span> <span>[</span><span>#temptb</span><span>]</span>
<span>50</span> <span>DROP</span> <span>TABLE</span> <span>[</span><span>#ttt</span><span>]</span></span>
View Code


我这个sql语句也需要拼接sql来达到LZ想要的效果

不过这篇文章的重点不是拼接SQL

重点是怎麽模仿游标

其实这个方法是最原始的方法，之前解决论坛问题的时候用过，想不到这次也能用上

SQLSERVER用无中生有的思想来替代游标SQLSERVER用无中生有的思想来替代游标 

<span>  1</span> <span>USE</span><span> tempdb
</span><span>  2</span> <span>GO</span>
<span>  3</span> 
<span>  4</span> <span>--</span><span>建表</span>
<span>  5</span> <span>CREATE</span> <span>TABLE</span><span> t1
</span><span>  6</span> <span>(
</span><span>  7</span>   client <span>VARCHAR</span>(<span>10</span><span>) ,
</span><span>  8</span>   pay_level <span>INT</span><span> ,
</span><span>  9</span>   pay_lv_1 <span>INT</span><span> ,
</span><span> 10</span>   pay_lv_2 <span>INT</span><span> ,
</span><span> 11</span>   pay_lv_3 <span>INT</span><span> ,
</span><span> 12</span>   pay_lv_4 <span>INT</span><span> ,
</span><span> 13</span>   pay_lv_5 <span>INT</span><span> ,
</span><span> 14</span>   pay_lv_6 <span>INT</span><span> ,
</span><span> 15</span>   pay_lv_7 <span>INT</span><span> ,
</span><span> 16</span>   pay_lv_8 <span>INT</span><span> ,
</span><span> 17</span>   pay_lv_9 <span>INT</span><span> ,
</span><span> 18</span>   pay_lv_10 <span>INT</span><span> ,
</span><span> 19</span>   pay_lv_11 <span>INT</span><span> ,
</span><span> 20</span>   pay_lv_12 <span>INT</span><span> ,
</span><span> 21</span>   pay_lv_13 <span>INT</span><span> ,
</span><span> 22</span>   pay_lv_14 <span>INT</span><span> ,
</span><span> 23</span>   pay_lv_15 <span>INT</span><span> ,
</span><span> 24</span>   pay_lv_16 <span>INT</span><span> ,
</span><span> 25</span>   pay_lv_17 <span>INT</span><span> ,
</span><span> 26</span>   pay_lv_18 <span>INT</span><span> ,
</span><span> 27</span>   pay_lv_19 <span>INT</span><span> ,
</span><span> 28</span>   pay_lv_20 <span>INT</span><span> ,
</span><span> 29</span>   pay_lv_21 <span>INT</span><span> ,
</span><span> 30</span>   pay_lv_22 <span>INT</span><span> ,
</span><span> 31</span>   pay_lv_23 <span>INT</span><span> ,
</span><span> 32</span>   pay_lv_24 <span>INT</span><span> ,
</span><span> 33</span>   pay_lv_25 <span>INT</span><span>,
</span><span> 34</span> <span>);
</span><span> 35</span> 
<span> 36</span> 
<span> 37</span> <span>--</span><span>插入测试数据</span>
<span> 38</span> <span>DECLARE</span> <span>@i</span> <span>INT</span>
<span> 39</span> <span>SET</span> <span>@i</span> <span>=</span> <span>1</span>
<span> 40</span> <span>WHILE</span> <span>@i</span> <span> <span>8</span> 
<span> 41</span>     <span>BEGIN</span>
<span> 42</span>         <span>INSERT</span>  <span>INTO</span><span> t1 ( client, pay_level, pay_lv_1, pay_lv_2, pay_lv_3,
</span><span> 43</span> <span>                           pay_lv_4, pay_lv_5, pay_lv_6, pay_lv_7, pay_lv_8,
</span><span> 44</span> <span>                           pay_lv_9, pay_lv_10, pay_lv_11, pay_lv_12,
</span><span> 45</span> <span>                           pay_lv_13, pay_lv_14, pay_lv_15, pay_lv_16,
</span><span> 46</span> <span>                           pay_lv_17, pay_lv_18, pay_lv_19, pay_lv_20,
</span><span> 47</span> <span>                           pay_lv_21, pay_lv_22, pay_lv_23, pay_lv_24,
</span><span> 48</span> <span>                           pay_lv_25 )
</span><span> 49</span>                 <span>SELECT</span>  <span>'</span><span>client</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@i</span> <span>AS</span> <span>VARCHAR</span>(<span>10</span><span>)),
</span><span> 50</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 51</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 52</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 53</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 54</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 55</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 56</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 57</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 58</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 59</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 60</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 61</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>(),
</span><span> 62</span>                         ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span>(), ( <span>20</span> <span>+</span> <span>1</span> ) <span>*</span> <span>RAND</span><span>()
</span><span> 63</span>           <span>SET</span> <span>@i</span><span>=</span><span>@i</span><span>+</span><span>1</span>
<span> 64</span> 
<span> 65</span>     <span>END</span>
<span> 66</span> 
<span> 67</span> <span>SELECT</span> <span>*</span> <span>FROM</span><span> t1
</span><span> 68</span> <span>GO</span>
<span> 69</span> 
<span> 70</span> <span>--</span><span>ALTER TABLE [t1] DROP COLUMN [pay_lv_2]</span>
<span> 71</span> 
<span> 72</span> 
<span> 73</span> <span>--</span><span>---------------------------------------------------</span>
<span> 74</span> <span>IF</span> <span>object_id</span>(<span>'</span><span>#ttt</span><span>'</span>) <span>IS</span> <span>NOT</span> <span>NULL</span>
<span> 75</span> <span>DROP</span> <span>TABLE</span><span> #ttt
</span><span> 76</span> <span>IF</span> <span>object_id</span>(<span>'</span><span>#temptb</span><span>'</span>) <span>IS</span> <span>NOT</span> <span>NULL</span>
<span> 77</span> <span>DROP</span> <span>TABLE</span><span> #temptb
</span><span> 78</span> 
<span> 79</span> <span>DECLARE</span> <span>@i</span> <span>INT</span>
<span> 80</span>   <span>--</span><span>用于循环的</span>
<span> 81</span> <span>SET</span> <span>@i</span> <span>=</span> <span>1</span>
<span> 82</span> <span>DECLARE</span> <span>@pay_level</span> <span>INT</span>
<span> 83</span>   <span>--</span><span>保存pay_level字段的值</span>
<span> 84</span> <span>DECLARE</span> <span>@COUNT</span> <span>INT</span>
<span> 85</span>    <span>--</span><span>保存t1表的总行数值</span>
<span> 86</span> <span>DECLARE</span> <span>@pay_lv</span> <span>INT</span>
<span> 87</span>   <span>--</span><span>用于保存pay_lv的值</span>
<span> 88</span> <span>DECLARE</span> <span>@sql</span> <span>NVARCHAR</span>(<span>2000</span><span>)
</span><span> 89</span> 
<span> 90</span> <span>CREATE</span> <span>TABLE</span> #ttt (ID <span>INT</span> <span>IDENTITY</span>(<span>1</span>,<span>1</span>), pay_cost <span>INT</span><span> )
</span><span> 91</span> 
<span> 92</span> <span>SELECT</span>  <span>IDENTITY</span>( <span>INT</span>,<span>1</span>,<span>1</span> ) <span>AS</span> ID, <span>*</span> <span>INTO</span>    #temptb <span>FROM</span><span>  t1
</span><span> 93</span> 
<span> 94</span> 
<span> 95</span> <span>--</span><span>获取t1表的总行数</span>
<span> 96</span> <span>SELECT</span>  <span>@COUNT</span> <span>=</span> <span>COUNT</span>(<span>*</span>) <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span>
<span> 97</span> <span>WHILE</span> <span>@i</span> <span> <span>@COUNT</span> 
<span> 98</span>     <span>BEGIN</span>
<span> 99</span>         <span>SELECT</span>  <span>@pay_level</span> <span>=</span> <span>[</span><span>pay_level</span><span>]</span> <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span> <span>WHERE</span>   id <span>=</span> <span>@i</span>
<span>100</span>     <span>--</span><span>判断列名是否存在，不存在就插入0</span>
<span>101</span>         <span>IF</span> <span>'</span><span>pay_lv_</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@pay_level</span> <span>AS</span> <span>VARCHAR</span>(<span>200</span>)) <span>IN</span> ( <span>SELECT</span>   NAME <span>FROM</span>     SYS.<span>[</span><span>syscolumns</span><span>]</span><span> ) 
</span><span>102</span>             <span>BEGIN</span>
<span>103</span>                 <span>--</span><span>用拼接sql的方法来获得pay_lv列对应的值，然后插入到#ttt表</span>
<span>104</span>                 <span>SET</span> <span>@sql</span> <span>=</span> N<span>'</span><span>select </span><span>'</span> <span>+</span> <span>'</span><span> @pay_lv=pay_lv_</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@pay_level</span> <span>AS</span> <span>NVARCHAR</span>(<span>200</span>)) <span>+</span> <span>'</span><span> from #temptb where id=</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@i</span> <span>AS</span> <span>NVARCHAR</span>(<span>20</span><span>))
</span><span>105</span>                 <span>EXEC</span> sp_executesql <span>@sql</span>, N<span>'</span><span>@pay_lv   int   output </span><span>'</span>, <span>@pay_lv</span><span> OUTPUT
</span><span>106</span>                 <span>INSERT</span>  <span>INTO</span> #ttt <span>VALUES</span>  (<span>@pay_lv</span><span>)
</span><span>107</span>             <span>END</span>
<span>108</span>         <span>ELSE</span> 
<span>109</span>             <span>BEGIN</span>
<span>110</span>                 <span>INSERT</span>  <span>INTO</span> #ttt <span>VALUES</span>(<span>0</span><span>)
</span><span>111</span>             <span>END</span>
<span>112</span>         <span>SET</span> <span>@i</span> <span>=</span> <span>@i</span> <span>+</span> <span>1</span>
<span>113</span>     <span>END</span>
<span>114</span> 
<span>115</span> 
<span>116</span> 
<span>117</span> <span>SELECT</span>  A.<span>[</span><span>client</span><span>]</span>, A.<span>[</span><span>pay_level</span><span>]</span>, B.<span>[</span><span>pay_cost</span><span>]</span>
<span>118</span> <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span> <span>AS</span><span> A
</span><span>119</span> <span>INNER</span> <span>JOIN</span> <span>[</span><span>#ttt</span><span>]</span> <span>AS</span> B <span>ON</span> A.<span>[</span><span>ID</span><span>]</span> <span>=</span> B.<span>[</span><span>ID</span><span>]</span>
<span>120</span> <span>ORDER</span> <span>BY</span> A.<span>[</span><span>ID</span><span>]</span> <span>ASC</span>
<span>121</span> 
<span>122</span> <span>DROP</span> <span>TABLE</span> <span>[</span><span>#temptb</span><span>]</span>
<span>123</span> <span>DROP</span> <span>TABLE</span> <span>[</span><span>#ttt</span><span>]</span></span></span>
View Code


关键代码有以下几句

<span> 1</span> <span>CREATE</span> <span>TABLE</span> #ttt (ID <span>INT</span> <span>IDENTITY</span>(<span>1</span>,<span>1</span>), pay_cost <span>INT</span><span> )
</span><span> 2</span> 
<span> 3</span> <span>SELECT</span>  <span>IDENTITY</span>( <span>INT</span>,<span>1</span>,<span>1</span> ) <span>AS</span> ID, <span>*</span> <span>INTO</span>    #temptb <span>FROM</span><span>  t1
</span><span> 4</span> 
<span> 5</span> <span>--</span><span>获取#t1表的总行数</span>
<span> 6</span> <span>SELECT</span>  <span>@COUNT</span> <span>=</span> <span>COUNT</span>(<span>*</span>) <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span>
<span> 7</span> <span>WHILE</span> <span>@i</span> <span> <span>@COUNT</span> 
<span> 8</span> <span>SELECT</span>  <span>@pay_level</span> <span>=</span> <span>[</span><span>pay_level</span><span>]</span> <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span> <span>WHERE</span>   id <span>=</span> <span>@i</span>
<span> 9</span> <span>SET</span> <span>@i</span> <span>=</span> <span>@i</span> <span>+</span> <span>1</span>
<span>10</span> <span>--</span><span>--------------------------------</span>
<span>11</span> <span>SELECT</span>  A.<span>[</span><span>client</span><span>]</span>, A.<span>[</span><span>pay_level</span><span>]</span>, B.<span>[</span><span>pay_cost</span><span>]</span>
<span>12</span> <span>FROM</span>    <span>[</span><span>#temptb</span><span>]</span> <span>AS</span><span> A
</span><span>13</span> <span>INNER</span> <span>JOIN</span> <span>[</span><span>#ttt</span><span>]</span> <span>AS</span> B <span>ON</span> A.<span>[</span><span>ID</span><span>]</span> <span>=</span> B.<span>[</span><span>ID</span><span>]</span>
<span>14</span> <span>ORDER</span> <span>BY</span> A.<span>[</span><span>ID</span><span>]</span> <span>ASC</span></span>

 

原表是没有自增id的，我建一个临时表#temptb，临时表有一个自增id，并把原表的数据全部放入临时表

获取临时表的行数，用于循环

每次执行的时候根据 WHERE   id = @i 来逐行逐行获取值，变量@i每次循环都递增1

将获取到的值都插入到#ttt这个临时表里面，然后根据ID的值做两表连接就可以得到LZ的结果

我说的无中生有就是“在原表里增加一个自增id方便循环，既简单又容易理解o(∩_∩)o ”

 

判断

我这里还用了一句

<span>1</span> <span>IF</span> <span>'</span><span>pay_lv_</span><span>'</span> <span>+</span> <span>CAST</span>(<span>@pay_level</span> <span>AS</span> <span>VARCHAR</span>(<span>200</span>)) <span>IN</span> ( <span>SELECT</span>   NAME <span>FROM</span>     SYS.<span>[</span><span>syscolumns</span><span>]</span> )

用于判断要获取值的pay_lv_列是否存在，如果存在就插入pay_lv_列的值，如果不存在就插入0

总结

其实如果觉得某样东西很难去实现，能不能用一个变通的方法呢？多动脑筋，办法会有的

 

如有不对的地方，欢迎大家拍砖o(∩_∩)o

성명
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MySQL 비동기 마스터 슬레이브 복제는 Binlog를 통한 데이터 동기화를 가능하게하여 읽기 성능 및 고 가용성을 향상시킵니다. 1) 마스터 서버 레코드는 Binlog로 변경됩니다. 2) 슬레이브 서버는 I/O 스레드를 통해 Binlog를 읽습니다. 3) 서버 SQL 스레드는 데이터를 동기화하기 위해 Binlog를 적용합니다.

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MySQL은 오픈 소스 관계형 데이터베이스 관리 시스템입니다. 1) 데이터베이스 및 테이블 작성 : CreateAbase 및 CreateTable 명령을 사용하십시오. 2) 기본 작업 : 삽입, 업데이트, 삭제 및 선택. 3) 고급 운영 : 가입, 하위 쿼리 및 거래 처리. 4) 디버깅 기술 : 확인, 데이터 유형 및 권한을 확인하십시오. 5) 최적화 제안 : 인덱스 사용, 선택을 피하고 거래를 사용하십시오.

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MySQL의 설치 및 기본 작업에는 다음이 포함됩니다. 1. MySQL 다운로드 및 설치, 루트 사용자 비밀번호를 설정하십시오. 2. SQL 명령을 사용하여 CreateAbase 및 CreateTable과 같은 데이터베이스 및 테이블을 만듭니다. 3. CRUD 작업을 실행하고 삽입, 선택, 업데이트, 명령을 삭제합니다. 4. 성능을 최적화하고 복잡한 논리를 구현하기 위해 인덱스 및 저장 절차를 생성합니다. 이 단계를 사용하면 MySQL 데이터베이스를 처음부터 구축하고 관리 할 수 ​​있습니다.

InnoDB 버퍼 풀은 어떻게 작동하며 성능에 중요한 이유는 무엇입니까?InnoDB 버퍼 풀은 어떻게 작동하며 성능에 중요한 이유는 무엇입니까?Apr 09, 2025 am 12:12 AM

innodbbufferpool은 데이터와 색인 페이지를 메모리에로드하여 MySQL 데이터베이스의 성능을 향상시킵니다. 1) 데이터 페이지가 버퍼 풀에로드되어 디스크 I/O를 줄입니다. 2) 더러운 페이지는 정기적으로 디스크로 표시되고 새로 고침됩니다. 3) LRU 알고리즘 관리 데이터 페이지 제거. 4) 읽기 메커니즘은 가능한 데이터 페이지를 미리로드합니다.

MySQL : 초보자를위한 데이터 관리의 용이성MySQL : 초보자를위한 데이터 관리의 용이성Apr 09, 2025 am 12:07 AM

MySQL은 설치가 간단하고 강력하며 데이터를 쉽게 관리하기 쉽기 때문에 초보자에게 적합합니다. 1. 다양한 운영 체제에 적합한 간단한 설치 및 구성. 2. 데이터베이스 및 테이블 작성, 삽입, 쿼리, 업데이트 및 삭제와 같은 기본 작업을 지원합니다. 3. 조인 작업 및 하위 쿼리와 같은 고급 기능을 제공합니다. 4. 인덱싱, 쿼리 최적화 및 테이블 파티셔닝을 통해 성능을 향상시킬 수 있습니다. 5. 데이터 보안 및 일관성을 보장하기위한 지원 백업, 복구 및 보안 조치.

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