How can I group time by hour or by 10 minutes?

Quick 'n dirty: One-size-fits-all for SQL dialects

The quick fixes above cater to SQL Server and PostgreSQL, but what about the party crashers like MySQL and Oracle? The alternative methods for these platforms are:

-- MySQL: Group by hour
SELECT EXTRACT(HOUR FROM your_column) AS Hour, COUNT(*) AS Total
FROM your_table
GROUP BY Hour; -- 'Hour' time is now!

-- MySQL: Group by 10-minute intervals
SELECT
    DATE_FORMAT(your_column, '%Y-%m-%d %H:%i') - INTERVAL (MINUTE(your_column) % 10) MINUTE AS TenMinGroup,
    COUNT(*) AS Total
FROM your_table
GROUP BY TenMinGroup;  -- 'Group' therapy for your data!

-- Oracle: Group by hour
SELECT TO_CHAR(your_column, 'HH24') AS Hour, COUNT(*) AS Total
FROM your_table
GROUP BY TO_CHAR(your_column, 'HH24'); -- Let me 'char' this for you!

-- Oracle: Group by 10-minute intervals
SELECT
    TRUNC(your_column, 'HH') + NUMTODSINTERVAL(FLOOR(TO_NUMBER(TO_CHAR(your_column, 'MI')) / 10) * 10, 'MINUTE') AS TenMinGroup,
    COUNT(*) AS Total
FROM your_table
GROUP BY TenMinGroup; -- Let's 'trunc' and roll!
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Lossless precision with timezone edge-cases

When grouping by intervals in high precision applications, it's crucial to strip milliseconds if not needed. Here's a snippet for SQL Server:

SELECT 
  DATEADD(MINUTE, (DATEDIFF(MINUTE, 0, your_column)/10)*10, 0) AS TenMinGroup,
  COUNT(*) AS Total
FROM your_table
GROUP BY 
  DATEADD(MINUTE, (DATEDIFF(MINUTE, 0, your_column)/10)*10, 0); -- Stripping milliseconds, because they 'second' best!


Do not overlook the importance of time zones and daylight saving time (DST). Make these a priority within SQL functionalities or via application logic, depending on the data context.

Custom interval grouping: DIY-style

Need to group by intervals that SQL functions aren't keen on? Bring in variables for bin size to spruce up your queries' flexibility.

DECLARE @BinSize INT = 10; -- Bin size in minutes for grouping

SELECT
  DATEADD(MINUTE, (DATEDIFF(MINUTE, 0, your_column)/@BinSize)*@BinSize, 0) AS CustomIntervalGroup,
  COUNT(*) AS Total
FROM your_table
GROUP BY 
  DATEADD(MINUTE, (DATEDIFF(MINUTE, 0, your_column)/@BinSize)*@BinSize, 0); -- Who needs off-the-shelf when you can DIY!


Secure performance for larger-than-life data

With mighty datasets spanning centuries, beware! Integer overflows can haunt your functions like DATEDIFF. Master anchor dates and date math strategies to make your SQL queries more long-lasting and robust.

Get over tricky corners and additional knacks

Let's fill up the odds and ends

While grouping sparse time data, some intervals may miss records. To fish out all intervals in your output, consider an outer join with a created series of time intervals.

Let's round up, not down

If you wish to round up rather than down, go ahead and use CEILING instead of FLOOR. This ensures that any pesky time value straddling the boundary belongs to the upper interval.

Nested queries - The matryoshka dolls of SQL

For more intricate requisites, such as varied grouping within the query or additional formatting, do not shy away from nested queries or common table expressions (CTEs) to break matters down into bite-sized pieces.