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You work at a freight shipping company with a large fleet of trucks. These trucks are based around the nation, with a mix of Mercedes and BMW models represented. The location of each truck that your company owns is stored as <code>(x,y)</code> coordinates in your database.

Given a list of locations that your trucks are stored at, return the top location <code>(x,y)</code> for each model of truck (Mercedes or BMW).

You can assume that there is one location with the most model of a truck, e.g. there will not be any locations that are tied for most BMWs stored.

Example:

Input:

<pre tabindex="0" class="chroma"><code>truck_locations = [{
 &#34;model&#34; : &#34;BMW&#34;,
 &#34;location&#34; : (1,2)
 },
 {
 &#34;model&#34; : &#34;Mercedes&#34;,
 &#34;location&#34; : (2,3)
 },
 {
 &#34;model&#34; : &#34;Mercedes&#34;,
 &#34;location&#34; : (2,2)
 },
 {
 &#34;model&#34; : &#34;Mercedes&#34;,
 &#34;location&#34; : (2,3)
 },
 {
 &#34;model&#34; : &#34;BMW&#34;,
 &#34;location&#34; = (1,2)
 },
 {
 &#34;model&#34; : &#34;BMW&#34;,
 &#34;location&#34; : (3,3)
 }
 ]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def truck_frequent_location(truck_locations) -&gt; { 
 &#34;Mercedes&#34; : (2,3), 
 &#34;BMW&#34; : (1,2) 
 }
}
</code></pre>

Explanation:

Mercedes repeated two times at location <code>(2,3)</code> and one time at the location <code>(2,2)</code>, so <code>(2,3)</code> is our most stored Mercedes location.

BMW repeated two times at location <code>(1,2)</code> and one time at the location <code>(3,3)</code>, so <code>(1,2)</code> is our most stored BMW location.

Given a list of locations that your trucks are stored at, return the top location for each model of truck (Mercedes or BMW).

Location Frequency

Let’s say we have a table with an <code>id</code> and <code>name</code> fields. The table holds over 100 million rows and we want to sample a random row in the table without throttling the database.

Write a query to randomly sample a row from this table.

Input:

<code>big_table</code> table

<table>
<thead>
<tr>
<th>Columns</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>

Write a query to randomly sample a row from a big table.

Random SQL Sample

Let’s say that your company is running a standard control and variant AB test on a feature to increase conversion rates on the landing page. The PM checks the results and finds a .04 p-value.

How would you assess the validity of the result?

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