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Asked: 2024-09-25T11:33:27+05:30 In:

“Counting Numbers in Defined Ranges Using SQL”

I came across this intriguing problem that involves SQL and ranges, and I can’t help but want to dive into it. So, here it is: let’s say you’ve got a table with numbers, and you need to group these numbers into ranges. The twist? You want to generate a list that not only shows each range but also counts how many numbers fall within each range.

Imagine you have a simple table called `Numbers`, structured like this:

“`
+——–+
| Number |
+——–+
| 1 |
| 2 |
| 3 |
| 5 |
| 7 |
| 10 |
| 12 |
| 15 |
| 20 |
+——–+
“`

Now, let’s say you want to group these numbers into ranges of 0-9, 10-19, and so on. So, from the above table, your expected output might look something like this:

“`
+———-+——-+
| Range | Count |
+———-+——-+
| 0-9 | 6 | (1, 2, 3, 5, 7)
| 10-19 | 4 | (10, 12, 15)
| 20-29 | 0 |
+———-+——-+
“`

The challenge is: how can you write a concise SQL query that accomplishes this? It has to be efficient because we’re working with potentially large datasets, and the output should dynamically reflect the number of ranges and the counts as the data changes.

I’d love to hear how you all would tackle this! What strategies or SQL functions would you consider? Also, how would you ensure that if a number falls outside of your specified range, it’s excluded correctly?

I’m curious about your solutions! Would using a common table expression (CTE) help? Or maybe some joins would make it easier? Let’s brainstorm together and see how creative we can get with SQL!

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    2 Answers



    1. SQL Ranges Problem

      Grouping Numbers into Ranges

      This problem is pretty interesting! Here’s how I think we can tackle it using SQL. It seems like we want to count how many numbers fall into specified ranges, right? Let’s try using a Common Table Expression (CTE) to make it easier to work with. Here’s a basic idea of how we could write the SQL query:

              
        WITH Ranges AS (
            SELECT
                CASE
                    WHEN Number BETWEEN 0 AND 9 THEN '0-9'
                    WHEN Number BETWEEN 10 AND 19 THEN '10-19'
                    WHEN Number BETWEEN 20 AND 29 THEN '20-29'
                    ELSE NULL
                END AS Range,
                Number
            FROM Numbers
        )
        SELECT
            Range,
            COUNT(Number) AS Count
        FROM Ranges
        WHERE Range IS NOT NULL
        GROUP BY Range
        ORDER BY MIN(Number);

      So, what this does is:

      • We define a Common Table Expression (CTE) named Ranges that assigns each number to a range based on its value.
      • Then, we select those ranges and count how many numbers fall into each one.
      • We filter out any ranges that are NULL (i.e., numbers outside our specified ranges) and group by the range to get our count.

      The results should show each range with the corresponding count of numbers that fall within that range, just like you wanted:

      Range Count
      0-9 6
      10-19 3
      20-29 0

      This should give you the output you’re after! I hope this helps with your SQL adventure!




    2. SQL Range Grouping

      To tackle the problem of grouping numbers into specified ranges and counting how many fall within each range using SQL, you can utilize a Common Table Expression (CTE) alongside the GROUP BY clause. Below is a SQL query that accomplishes this task efficiently. The query first defines the ranges using a CTE and then counts how many numbers fall into those ranges by using a LEFT JOIN to include any ranges that have a count of zero.

      
WITH Ranges AS (
    SELECT 0 AS start_range, 9 AS end_range
    UNION ALL
    SELECT 10, 19
    UNION ALL
    SELECT 20, 29
)
SELECT 
    CONCAT(start_range, '-', end_range) AS Range,
    COUNT(n.Number) AS Count
FROM 
    Ranges r
LEFT JOIN 
    Numbers n ON n.Number BETWEEN r.start_range AND r.end_range
GROUP BY 
    r.start_range, r.end_range
ORDER BY 
    r.start_range;

      This query effectively constructs the desired output, showing each range alongside the count of numbers that fall within that range. The use of BETWEEN ensures that any numbers falling outside the defined ranges are excluded from the count. By leveraging a CTE for the ranges, you can easily modify or extend the ranges without restructuring the entire query.


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