What is the best way to store a duration in MySQL?

 Storing a duration in MySQL depends on the nature of the durations you need to store and the kinds of queries you intend to run. Here are some common approaches:

1. Use an INT to Store the Duration in Seconds

• Description: Store the duration as the total number of seconds.
• Advantages:
  • Simple to store and retrieve.
  • Easy to perform arithmetic operations (e.g., summing durations).
  • Saves storage space (4 bytes for INT).
• Use Case: When you need to calculate total durations, compare durations, or don't need to display durations in a human-readable format directly.
• Example:

  CREATE TABLE durations (
      id INT AUTO_INCREMENT PRIMARY KEY,
      duration_seconds INT NOT NULL
  );
  

2. Use a TIME Data Type

• Description: Store the duration as a time value (e.g., HH:MM:SS).
• Advantages:
  • Human-readable format for durations.
  • Built-in time functions in MySQL can be used (e.g., TIME_TO_SEC, SEC_TO_TIME).
• Limitations:
  • Maximum value is 838:59:59 (slightly over 34 days).
  • Less intuitive for durations exceeding a day.
• Use Case: When you want to store durations under 35 days and need a readable format.
• Example:

  CREATE TABLE durations (
      id INT AUTO_INCREMENT PRIMARY KEY,
      duration TIME NOT NULL
  );
  

3. Store as an ISO 8601 Duration String

• Description: Use a VARCHAR column to store durations in ISO 8601 format (e.g., PT2H30M for 2 hours and 30 minutes).
• Advantages:
  • Standardized format that supports complex durations (e.g., years, months, days).
  • Compatible with systems that use ISO 8601 durations.
• Limitations:
  • Harder to perform calculations without converting the string to another format.
  • Larger storage space required.
• Use Case: When interoperability with external systems is critical.
• Example:

  CREATE TABLE durations (
      id INT AUTO_INCREMENT PRIMARY KEY,
      duration VARCHAR(20) NOT NULL
  );
  

4. Use a DATETIME or TIMESTAMP Pair

• Description: Store the start and end times as two separate DATETIME or TIMESTAMP columns.
• Advantages:
  • Provides both the duration and context of when the event occurred.
  • Can handle durations of any length.
• Limitations:
  • Requires additional computation to calculate the duration (TIMESTAMPDIFF).
  • Takes more storage space (two DATETIME fields).
• Use Case: When you need both the duration and the associated time range.
• Example:

  CREATE TABLE durations (
      id INT AUTO_INCREMENT PRIMARY KEY,
      start_time DATETIME NOT NULL,
      end_time DATETIME NOT NULL
  );
  

Recommendation

• For simplicity and flexibility, use an INT to store the duration in seconds if you only care about the duration value.
• If human-readability or built-in time functions are important, use the TIME data type.
• Choose the appropriate option based on the trade-offs that suit your application's needs.