datetime Archives - SQLPerformance.com

Dealing with date and time instead of datetime

Rob Farley describes a tactic where adding multiple predicates around separate date and time columns can win you some better performance.

Rob Farley ◆ March 29, 2018

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Trimming time from datetime – a follow-up

Aaron Bertrand follows up on an earlier post about trimming time from datetime, this time examining the performance characteristics of various methods without data access.

Aaron Bertrand ◆ October 25, 2012

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How much impact can a data type choice have?

I've long been a proponent of choosing the correct data type. I've talked about some examples in a previous "Bad Habits" blog post, but this weekend at SQL Saturday #162 (Cambridge, UK), the topic of using DATETIME by default came up. In a conversation after my T-SQL : Bad Habits and Best Practices presentation, a user stated that they just use DATETIME even if they only need granularity to the minute or day, this way the date/time columns across their enterprise are always the same data type. I suggested that this might be wasteful, and that the consistency might not be worth it, but today I decided to set out to prove my theory.

Aaron Bertrand ◆ September 13, 2012

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What is the most efficient way to trim time from datetime?

The most common need for stripping time from a datetime value is to get all the rows that represent orders (or visits, or accidents) that occurred on a given day. However, not all of the techniques that are used to do so are efficient or even safe. If you want a safe range query that performs well, use an open-ended range or, for single-day queries on SQL Server 2008 and above, use CONVERT(DATE). Read on to discover why…

Aaron Bertrand ◆ September 5, 2012

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