Datetime in where clause

Deep talk on datetime filtering

Getting precise with your datetime search? Don the cap of specificity. Here's how:

Range Queries like a Pro

The golden rule? 'YYYYMMDD' always. It is bulletproof against quirky SQL Server locale changes. Here's how you range for a full day:

WHERE datetime_field >= '20220914' AND datetime_field < '20220915'; -- 24 hours later
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You get the day up to 23:59:59.999. Neat, huh?

The BETWEEN Gotcha

BETWEEN is great— until it's not. It's an inclusive operator, and slips in the end date:

WHERE datetime_field BETWEEN '20220914' AND '20220915'; -- Hey, the 15th sneaked in!
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Time Granularity Alert

Latching onto milliseconds? Keep SQL Server's time field precision in mind:

WHERE datetime_field < '20220915 00:00:00.000'; -- To infinity, but not beyond!
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Embrace Indexed Computed Columns

QuarterBack the performance: Add computed columns for DAY, MONTH, YEAR. Persist and index them. Say hello to speed.

The ISO-8601 Assurance

Cross-platform? Cross-language? Use the ISO-8601 format. It's your armor against locale changes:

WHERE datetime_field = '2022-09-15T12:00:00Z';
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The Practical Cases Checklist

Gearing at Start of Day

Get to the day's start with an exact timestamp:

WHERE datetime_field >= '20220914 00:00:00.000'; -- The rooster crows
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Focus on Date, Not Time

Discard time like yesterday’s newspaper with CAST:

WHERE CAST(datetime_field AS DATE) = '20220914'; -- Time flies anyway
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The Titbits of Convertibles

SQL Server's CONVERT syntax rolls with some gremlins. When unsure, resort to {d 'yyyy-mm-dd'} for literals and peek at the MSDN.

Deal with a Specific Day

Ditch the time, focus on the day:

WHERE CONVERT(DATE, datetime_field) = '20220914';
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Think of Fractional Seconds

Remember, milliseconds aren't just fillers:

WHERE datetime_field BETWEEN '20220914 00:00:00.000' AND '20220914 23:59:59.997'; -- Every millisecond counts!
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Performance Is Key

Functions like DAY(), MONTH(), YEAR() can cause table scans. When performance is king, persistent, indexed columns can be your knights in shining armor.