When Comparing Dates with MySQL\'s DATE_FORMAT, Why Is Using the Same Format Crucial?

Date Comparison with MySQL DATE_FORMAT

When comparing dates using MySQL's DATE_FORMAT function, it's crucial to understand that the format you choose affects the comparison outcome.

In the given example, the table contains dates formatted as '%d-%m-%Y', and the query attempts to compare them using the same format. However, this leads to incorrect results because "28-10-2012" is lexicographically greater than "02-11-2012".

To resolve this, it's recommended to compare dates as dates rather than strings. The correct query should be:

<code class="mysql">select date_format(date(starttime),'%d-%m-%Y') from data
where date(starttime) >= date '2012-11-02';</code>

Here, the date() function extracts the date component from the starttime field, while date '2012-11-02' specifies the comparison date in year-month-value form. This ensures that the comparison is done correctly as dates.

If starttime is a DATETIME field, consider using the following query to avoid repeated conversion:

<code class="mysql">select date_format(date(starttime),'%d-%m-%Y') from data
where starttime >= '2012-11-02 00:00:00';</code>

In general, it's advisable to use the ISO-8601 standard for date formatting, such as y-M-d. However, the above queries demonstrate how to perform date comparisons using the provided format.

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