SQL更新查询通过连接3个表来获取值

Question

请帮我写下面的更新查询。我正在使用SQL Server 2014.

要求：根据项目ID更新表C，为对应项目ID和最新记录获取对应的'Answer_weightage'值。表A'最新'='是'表示这是最新记录。基于'Link_Id'表A和B是链接的。表A和C是根据 'PROJECT_ID'

表A联：

<table> 
 
<tr> 
 
<th> 
 
Request Type | 
 
</th> 
 
<th>Project ID | </th> 
 
<th>Latest |</th> 
 
<th> \t Link_ID</th> 
 
</tr> 
 
<tr> 
 
----------------------------------------------- 
 
</tr> 
 
<tr> 
 
<td> 
 

 
a \t 
 
</td> 
 
<td>1000</td> \t <td>No</td> \t <td>1</td> 
 
</tr> 
 
<tr> 
 
<td>b</td> \t <td>1005</td> \t <td>Yes </td>  \t <td>2</td> 
 
<tr> 
 
<td>123</td> \t <td>1000</td><td>Yes </td>  \t <td>4</td></tr> 
 
<tr> 
 
<td>c \t </td><td>1005</td> \t <td>No</td> \t <td>3</td></tr> 
 
</table>

表B

<table> 
 
<tr> 
 
<th> 
 
Question</th> \t <th>Description</th> \t <th>Answer_weightage</th> \t <th>Link_ID 
 
</th> 
 

 
</tr> 
 

 
<tr><td> 
 
6 \t </td><td>Question6 \t </td><td>0</td> \t <td>2</td> 
 
</tr> 
 
<tr> 
 
<td>2</td> \t <td>Question2</td> \t <td>5</td> \t <td>4</td></tr> 
 
<tr> 
 
<td>3</td> \t <td>Question3 \t </td><td>5</td> \t <td>4</td></tr> 
 
<tr> 
 
<td>4</td> \t <td>Question4</td><td> \t 5</td> \t <td>4</td></tr> 
 
<tr> 
 
<td>5 \t </td><td>Question5 \t </td><td>2</td> \t <td>4</td></tr> 
 
<tr> 
 
<td>6</td> \t <td>Question6 \t </td><td>2 \t </td><td>4</td></tr> 
 
<tr> 
 
<td>7</td> \t <td>Question7</td> \t <td>9 \t </td><td>4</td></tr> 
 
<tr> 
 
<td>1</td> \t <td>Question1 \t </td><td>5</td> \t <td>1</td></tr> 
 
<tr> 
 
<td>2</td> \t <td>Question2 \t </td><td>9</td> \t <td>1</td></tr> 
 
<tr> 
 
<td>3 \t </td><td>Question3 \t </td><td>5</td><td> \t 1</td></tr> 
 
<tr> 
 
<td>4</td> \t <td>Question4</td> \t <td>2 \t </td><td>1</td></tr> 
 
<tr> 
 
<td>5</td> \t <td>Question5</td> \t <td>5 \t </td><td>1</td></tr> 
 
<tr> 
 
<td>6</td> \t <td>Question6</td> \t <td>5 \t </td><td>1</td></tr> 
 
<tr> 
 
<td>7</td> \t <td>Question7</td> \t <td>2</td> \t <td>1</td></tr> 
 
<tr> 
 
<td>1</td> \t <td>Question1</td> \t <td>2 \t </td><td>2</td></tr> 
 
<tr> 
 
<td>2</td> \t <td>Question2</td> \t <td>0 \t </td><td>2</td></tr> 
 
<tr> 
 
<td>3 \t </td><td>Question3</td> \t <td>9 \t </td><td>2</td></tr> 
 
<tr> 
 
<td>4</td> \t <td>Question4 \t </td><td>9</td><td> \t 2</td></tr> 
 
<tr> 
 
<td>5 \t </td><td>Question5 \t </td><td>9</td><td> \t 2</td></tr> 
 
<tr> 
 
<td>7 \t </td><td>Question7</td> \t <td>5 \t </td><td>2</td></tr> 
 
<tr> 
 
<td>1</td> \t <td>Question1</td><td> \t 2</td> \t <td>4</td></tr> 
 

 
</table>

表C：

<table> 
 
<tr> 
 
<th>Project ID</th> 
 
<th>Question1</th> 
 
<th>Question2</th> 
 
<th>Question3</th> 
 
<th>Question4</th> 
 
<th>Question5</th> 
 
<th>Question6</th> 
 
<th>Question7</th> 
 
</tr> 
 
<tr> 
 
<td>1000</td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
</tr> 
 
<tr> 
 
<td>1005</td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
<td></td> 
 
</tr> 
 
</table>

所需的结果（表C）：

<table> 
 
    <tr> 
 
    <th>Project ID</th> 
 
    <th>Question1</th> 
 
    <th>Question2</th> 
 
    <th>Question3</th> 
 
    <th>Question4</th> 
 
    <th>Question5</th> 
 
    <th>Question6</th> 
 
    <th>Question7</th> 
 
    </tr> 
 
    <tr> 
 
    <td>1000</td> 
 
    <td>2</td> 
 
    <td>5</td> 
 
    <td>5</td> 
 
    <td>5</td> 
 
    <td>2</td> 
 
    <td>2</td> 
 
    <td>9</td> 
 
    </tr> 
 
    <tr> 
 
    <td>1005</td> 
 
    <td>2</td> 
 
    <td>0</td> 
 
    <td>9</td> 
 
    <td>9</td> 
 
    <td>0</td> 
 
    <td>9</td> 
 
    <td>5</td> 
 
    </tr> 
 
    </table>

Answer 1

要更新表C的question1，将值设置为等于从B中选择的Answer_weightage，其中b.Description ='Question1'和linkId =（Link_Id from A where latest ='YES'并且与C具有相同的projectId ）。

Update C set C.Question1 = 
(select Answer_weightage 
    from B 
    where Description='Question1' and Link_ID = 
     (select Link_ID 
      from A 
      where A.ProjectID = C.ProjectID and Latest='Yes'))