MySQL PHP - How to group and count records by value ranges with upper limit

Other Questions MySQL
1

I’m working on a feature that analyzes message length and success rates. When someone types 250 characters, I need to find the success rate for all previous users who typed between 210-290 characters.

I have this MySQL query that works:

SELECT 
  COUNT(*) AS record_count, 
  SUM(success_flag) AS successful_records, 
  (SUM(success_flag) / COUNT(*)) * 100 AS success_percentage, 
  message_length
FROM user_data 
WHERE message_length IS NOT NULL
GROUP BY message_length div 50

The problem is with longer messages. When message_length goes above 500 characters, I want to group all those high values into one single bucket instead of creating separate groups.

Is there a way to modify this query so values above a threshold get combined? Any better approach would be appreciated too.

2

Use a CASE statement to cap your grouping logic. Instead of just dividing by 50, create a conditional that treats everything above 500 as the same group.

Modify your GROUP BY like this:

SELECT 
  COUNT(*) AS record_count, 
  SUM(success_flag) AS successful_records, 
  (SUM(success_flag) / COUNT(*)) * 100 AS success_percentage,
  CASE 
    WHEN message_length > 500 THEN 500
    ELSE (message_length DIV 50) * 50
  END AS length_group
FROM user_data 
WHERE message_length IS NOT NULL
GROUP BY CASE 
  WHEN message_length > 500 THEN 500
  ELSE message_length DIV 50
END

This lumps all messages over 500 characters into one bucket while keeping your 50-character intervals for shorter messages. The length_group column shows the actual range boundaries, making results easier to read when analyzing data.

3

Use a calculated column to handle the grouping logic before your main query runs. Wrap your existing logic in a subquery and apply the threshold condition there.

SELECT 
  COUNT(*) AS record_count,
  SUM(success_flag) AS successful_records,
  (SUM(success_flag) / COUNT(*)) * 100 AS success_percentage,
  bucket_group
FROM (
  SELECT 
    success_flag,
    IF(message_length > 500, 10, message_length DIV 50) AS bucket_group
  FROM user_data 
  WHERE message_length IS NOT NULL
) AS bucketed_data
GROUP BY bucket_group

The IF function throws anything over 500 characters into bucket 10, while shorter messages get their normal division grouping. Your original math stays the same but everything above the limit gets forced into one bucket. You’ll probably want to tweak that bucket number (10) based on how many regular buckets you’re expecting.