Combining Multiple Values into a Single Count using SQL's CASE Statement

SQL: Combining Multiple Values into a Single Count

In this article, we will explore how to combine multiple values from a table into a single count in SQL. We will start by examining the given scenario and then dive into the solution using a CASE statement.

Scenario Overview

We have a table called Browsers with two columns: BrowserName and Date. The table is populated every time a browser is opened, along with the associated date. Our goal is to combine multiple values from this table into a single count in SQL.

Current Query

Let’s take a look at our current query:

SELECT 
    COUNT (BrowserName) AS [Count Of Uses],
    BrowserName AS [Browser],
    Date
FROM 
    BROWSERS
GROUP BY 
    Date, BrowserName;

This query groups the data by Date and BrowserName, which results in multiple entries for each browser. However, we want to combine these values into a single count.

Problem Statement

Notice that there are two entries for Firefox: one with the exact name Firefox and another with the name Firefox?. We want to combine these into a single entry for Firefox, resulting in the following desired output:

Count Of Uses       Browser             Date
--------------------------------------------------
       2            Firefox             8/20/2017
       3            Google Chrome       8/20/2017
       2            Internet Explorer   8/20/2017
       1            Opera               8/20/2017

Solution Overview

To achieve this, we can use a CASE statement in SQL. The idea is to check if the BrowserName matches a specific pattern (in this case, starting with Firefox) and return either the full browser name or an alias.

Using CASE Statement

Here’s how we can modify our query to use a CASE statement:

SELECT 
    Date,
    (CASE WHEN BrowserName LIKE 'Firefox%' THEN 'Firefox'
          ELSE BrowserName
     END) as Browser,
    COUNT(*) AS [Count Of Uses]
FROM BROWSERS
GROUP BY Date,
         (CASE WHEN BrowserName LIKE 'Firefox%' THEN 'Firefox'
               ELSE BrowserName
          END);

Let’s break down what’s happening here:

We’re using the LIKE operator to check if the BrowserName starts with Firefox.
If it does, we return 'Firefox'. Otherwise, we return the original BrowserName.
We’re grouping by both the Date and the alias of the BrowserName, which effectively combines the values.

How It Works

Here’s a step-by-step explanation:

The query groups the data by Date and the alias of the BrowserName.
For each group, it checks if the original BrowserName starts with 'Firefox'. If true:
- It returns 'Firefox' as the alias.
Otherwise, it keeps the original BrowserName.

Conclusion

In this article, we learned how to combine multiple values from a table into a single count using SQL’s CASE statement. By leveraging pattern matching and conditional logic, we can effectively group data and simplify our queries.