获取平均值并加入3个表

Question

我有3张表格，如下所示;

用户表：

<table border="1">
<tr>
<td>uid</td>
<td>name</td>
<td>status</td>
<td>category</td>
</tr>
<tr>
<td>1</td>
<td>John Doe</td>
<td>1</td>
<td>C</td>
</tr>
<tr>
<td>2</td>
<td>Jane Doe</td>
<td>1</td>
<td>C</td>
</tr>

</table>

个人资料表：

<table border="1">
<tr>
<td>pid</td>
<td>uid</td>
<td>slug</td>
</tr>
<tr>
<td>1</td>
<td>1</td>
<td>john-doe</td>
</tr>
<tr>
<td>2</td>
<td>2</td>
<td>jane-doe</td>
</tr>
</table>

评级表：

<table border="1">
<tr>
<td>rid</td>
<td>uid</td>
<td>rating</td>
</tr>
<tr>
<td>1</td>
<td>1</td>
<td>3.5</td>
</tr>
<tr>
<td>2</td>
<td>1</td>
<td>2.5</td>
</tr>
<tr>
<td>3</td>
<td>2</td>
<td>3.5</td>
</tr>
<tr>
<td>4</td>
<td>1</td>
<td>2.5</td>
</tr>

<tr>
<td>5</td>
<td>2</td>
<td>3.5</td>
</tr>
<tr>
<td>6</td>
<td>2</td>
<td>2.5</td>
</tr>


<tr>
<td>7</td>
<td>1</td>
<td>3.5</td>
</tr>
<tr>
<td>8</td>
<td>2</td>
<td>2.5</td>
</tr>
</table>

我正在尝试加入该表，并从评级表评级表中获得具有平均id和avg评级的值。

我想要的输出如下;

<table border="1">
<tr>
<td>uid</td>
<td>name</td>
<td>slug</td>
<td>status</td>
<td>category</td>
<td>rating</td>
</tr>
<tr>
<td>1</td>
<td>John Doe</td>
<td>john-doe</td>
<td>1</td>
<td>C</td>
<td>3.25</td>
</tr>

<tr>
<td>2</td>
<td>Jane Doe</td>
<td>jane-doe</td>
<td>1</td>
<td>C</td>
<td>3</td>
</tr>


</table>

Answer 1

请尝试以下查询，我认为这对您有用。

  

选择你。*，p.slug，（从评级r中选择平均值（评级），其中r.uid = u.uid）作为评级来自用户你加入个人资料p ON p.uid = u.uid