How to Efficiently Extract Dates from DateTime Columns in MySQL?

Efficiently Selecting Dates from Datetime Columns

When working with datetime data types, it can often be necessary to extract specific components, such as dates or times. This article addresses the challenge of retrieving dates from datetime columns in MySQL.

The Issue

A common query is to filter rows based on a specific date, as in the following example:

SELECT * FROM data
WHERE datetime = '2009-10-20'
ORDER BY datetime DESC;

However, the provided solution of using a BETWEEN clause to define a date range of '2009-10-20 00:00:00' to '2009-10-20 23:59:59' returns an empty result set.

The Solution

To extract dates effectively, MySQL provides the DATE() function, which returns the date component of a datetime value. Using DATE() in the WHERE clause allows for direct comparison with a date literal:

SELECT * FROM data
WHERE DATE(datetime) = '2009-10-20'
ORDER BY datetime DESC;

An alternative approach that can sometimes improve performance is to use the LIKE operator with a wildcard suffix:

SELECT * FROM data
WHERE datetime LIKE '2009-10-20%'

However, it's crucial to note that LIKE comparisons may have performance implications, as discussed in other Stack Exchange threads.

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