Sql ORDER BY date problem

sql

date-format

sql-performance

best-practices

byNikita Barsukov·Sep 26, 2024

Before ascending the stairway to heaving with your data, your column should be in a proper DATE or DATETIME type, not a string. Use CAST to shape-shift it into a date and control its sorting destiny like a pro.

SELECT *
FROM names_of_ancients   -- let's pretend your_table is this names_of_ancients
ORDER BY CAST(when_they_died AS DATE); -- here the date_column is when_they_died

Change names_of_ancients and when_they_died as per your table and column names. This will set your dates in immaculate order, as the universe intended.

Not juggling, just converting

Storing dates as plain 'ol strings can backfire when you attempt a Gandalf-level neat trick to sort them in SQL. Apply CAST([your_column] AS DATETIME), and voila it becomes date and time. If you have more specific ambitions, use CONVERT(DATETIME, [your_column], [style]), where [style] corresponds to a code representing the date format (e.g., 103 for dd/MM/yyyy).

Time is an illusion. Lunchtime, doubly so. So is your date format.

Keep a sharp eye on the format of your date columns. Check if the dates are lounging on a Challenger Deep trench or chilling on the peak of Everest based on regional settings. Stick to the safe terrain of the yyyy/MM/dd format for a date column, where the yyyy, MM and dd sing in harmony to the tune of natural order.

Performance: More date, less vent

Minimize date conversions to give your database performance a Red Bull boost. When in doubt, head over to MSDN or equivalent documentation for the right form of the patronus charm against incorrect syntax. When designing your tables, opt for a DATE type for dates. As you will learn, anticipation is the mother of fast databases.

Making sense of chaos

Problems arise when the date strings have been sprinkled by a prankster instead of an ISO-compliant machine. Use the right format code with CONVERT to finally bring order to your table. It's like giving that prankster a time-out and calling in a librarian to arrange your books.

ORDER BY CONVERT(DATETIME, your_date_column, 105) -- 105 like a high five given to an ordering problem

Examine your ORDER BY clauses and match them with the actual date values on your table. Misalignments here can lead to incorrect sorting or you may summon an unholy error beast.

Steering clear of common traps

A query likes to keep in shape. Using functions in the order by column makes it sluggish, making full table scans a habit. Instead, let it do some cardio with covered indexes. Give thought to how your UNION clauses or window functions could disrupt your peaceful date ordering. Always stick to a consistent date format for harmonious results. Lastly, don't fear to test your queries against different date inputs to catch any hiccups.

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