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Asked: 2024-09-25T05:02:11+05:30 In:

How can I perform a subtraction between two datetime columns in SQLite to find the difference in time between them?

I’ve been dabbling with SQLite for a little project I’m working on, and I’ve hit a bit of a roadblock with date and time calculations. So, I have two datetime columns in my table, let’s say one is called `start_time` and the other is `end_time`. I need to find out the difference between these two timestamps because I’m trying to calculate how long a certain event lasted.

Here’s the catch: I’ve read a bunch of documentation and tutorials, but whenever I try to subtract one datetime from the other, I end up getting results that don’t make sense. Sometimes, it looks like it’s returning the raw numbers instead of giving me something more readable like hours or minutes. I really want to get a better grip on how to extract that information correctly.

What I thought was simple arithmetic has really turned into a bit of a headache. I’m assuming there’s a straightforward way to do this in SQLite, but I might just be missing the right syntax or function. Can someone explain to me how to perform this subtraction the right way?

If you could lay it out step-by-step, or at least suggest the functions I should be looking into, that would be fantastic. Also, it would be great if you could provide an example query or two.

And just for context, I don’t need the milliseconds or anything super detailed. A simple output of the difference in hours and minutes would be perfect. Any insights or tips would be greatly appreciated! It feels like the more I read, the more confused I get – so I could really use some clarification from someone who’s been there before. Thanks in advance!

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    2 Answers


    1. Okay, I get what you’re going through! Date and time calculations can be tricky in SQLite, but I’ve got your back.

      To find the difference between two datetime columns (`start_time` and `end_time`), you can use the `strftime` function to convert the time into a readable format. Here’s a simple way to do it step-by-step:

      1. Make sure your datetime columns are in a format SQLite recognizes (like ISO 8601: “YYYY-MM-DD HH:MM:SS”).
      2. You can calculate the difference in seconds using `julianday()` function, which is super handy for date calculations.
      3. After that, you can convert the seconds into hours and minutes as you like!

      Here’s a query that shows how to do it:

            
        SELECT 
          start_time, 
          end_time,
          (julianday(end_time) - julianday(start_time)) * 24 AS hours,
          ((julianday(end_time) - julianday(start_time)) * 24 * 60) % 60 AS minutes
        FROM events;  -- Replace 'events' with your table name

      In this query:

      • The difference is calculated in days (thanks to `julianday`), and then we multiply by 24 to get hours.
      • To get minutes, we multiply the difference by 24 (to get hours) and then multiply by 60 to convert to minutes. Using `% 60` gives you the remainder after dividing by 60, so you only get the minutes part.

      That should provide a result that shows you how many hours and minutes your event lasted! Just replace `events` with the name of your table, and you should be good to go.

      Hope that clears things up a bit! Good luck with your project!



    2. To calculate the duration between two datetime columns, `start_time` and `end_time`, in SQLite, you can utilize the built-in `strftime` function along with simple arithmetic. The key is to convert the datetime values into a format that you can manipulate easily, such as by counting the total seconds between the two timestamps. You can achieve this using the `julianday` function, which returns the Julian day numbers. For example, you can compute the difference in seconds by subtracting the Julian day numbers of the two timestamps, multiplying the result by 86400 (the number of seconds in a day):
      SELECT (julianday(end_time) - julianday(start_time)) * 86400 AS duration_seconds FROM your_table;. Once you have the duration in seconds, you can further break it down into hours and minutes.

      To convert the total duration in seconds to a more readable format, you can use integer division and the modulus operator. Here’s a full example of how this can be done in a single query:
      SELECT
      (julianday(end_time) - julianday(start_time)) * 86400 AS duration_seconds,
      ((julianday(end_time) - julianday(start_time)) * 86400) / 3600 AS duration_hours,
      ((julianday(end_time) - julianday(start_time)) * 86400) % 3600 / 60 AS duration_minutes
      FROM your_table;       This will give you the total duration in seconds, hours, and minutes directly from your query. With that, you should be able to get a clear view of how long your events lasted without the confusion of raw numbers.


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