Understanding SQL and Retrieving Top 3 Business Categories with Search Volume

In this article, we’ll delve into the world of SQL and explore how to retrieve the top 3 business categories based on their search volume. We’ll break down the process step by step, discussing various concepts such as subqueries, grouping, and limiting results.

Introduction to SQL

SQL (Structured Query Language) is a standard language for managing relational databases. It’s used to store, manipulate, and retrieve data in these databases. SQL is divided into several components, including:

SELECT: Retrieves data from one or more tables.
FROM: Specifies the table(s) to retrieve data from.
WHERE: Filters data based on specific conditions.
GROUP BY: Groups data based on one or more columns.
HAVING: Filters grouped data based on aggregated values.

Understanding the Problem

The problem at hand is to retrieve the top 3 business categories in a database, along with their corresponding search volume. The query provided attempts to achieve this by selecting the top searches for each category and then displaying them as a table.

However, there are several issues with the original query:

It doesn’t use subqueries correctly.
It groups data based on ASC instead of searching for the maximum value.
It uses LIMIT 3, which can lead to inaccurate results if the top 3 categories don’t have the same number of rows.

Correcting the Query

To fix these issues, we’ll use a subquery to first find the top search volume for each category and then retrieve those specific rows from the original table. Here’s an example query:

SELECT search, city, business, COUNT(*) AS total
FROM vendor
WHERE category = 'Beauty Salon'
GROUP BY search, city, business
ORDER BY total DESC
LIMIT 3;

However, this query still has limitations:

It groups data based on search, city, and business. However, we want to display the top searches for each category separately.
We need to ensure that the results are ordered by the maximum search volume.

Improved Query

To overcome these challenges, let’s use a subquery to first find the maximum search volume for each category. Here’s an updated query:

SELECT *
FROM (
  SELECT category, MAX(total) AS max_total, search, city, business
  FROM (
    SELECT search, city, business, COUNT(*) AS total
    FROM vendor
    WHERE category = 'Beauty Salon'
    GROUP BY search, city, business
  ) t
) subquery
WHERE subquery.max_total = subquery.search + subquery.city + subquery.business;

This query uses a subquery to find the maximum search volume for each category. The outer query then selects only those rows where the total count equals the sum of search, city, and business.

Displaying Results

Once we have retrieved the top 3 business categories with their corresponding search volume, we can display them as a table:

<table class="demo">
  <thead>
    <tr class="titledemo" align="left">
      <th width="25%"">Ranking</th>
      <th width="25%">Business</th>
      <th width="25%">Searches</th>
      <th width="25%">Category</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>1</td>
      <td>
        <strong><?php echo $row["business"]; ?></br></strong>
      </td>
      <td>
        <?php echo $row["search"]; ?><br>
      </td>
      <td>
        <?php echo $row["city"]; ?><br>
      </td>
    </tr>
  </tbody>
</table>

Conclusion

Retrieving the top 3 business categories based on their search volume is a relatively straightforward task in SQL. By using subqueries, grouping data correctly, and limiting results, we can ensure accurate and reliable results.

Understanding how to use these concepts will help you tackle similar challenges in your own SQL queries. Remember to always consider the specifics of your database schema when crafting your query, and don’t hesitate to experiment with different approaches until you find one that works for you.

Last modified on 2025-04-05