How to select date from datetime column? - mysql

Question

I have a column of type "datetime" with values like 2009-10-20 10:00:00
I would like to extract date from datetime and write a query like:
SELECT * FROM
data
WHERE datetime = '2009-10-20'
ORDER BY datetime DESC
Is the following the best way to do it?
SELECT * FROM
data
WHERE datetime BETWEEN('2009-10-20 00:00:00' AND '2009-10-20 23:59:59')
ORDER BY datetime DESC
This however returns an empty resultset. Any suggestions?

Answer 1

You can use MySQL's DATE() function:
WHERE DATE(datetime) = '2009-10-20'
You could also try this:
WHERE datetime LIKE '2009-10-20%'
See this answer for info on the performance implications of using LIKE.

Answer 2

Using WHERE DATE(datetime) = '2009-10-20' has performance issues. As stated here:
it will calculate DATE() for all rows, including those that don't match.
it will make it impossible to use an index for the query.
Use BETWEEN or >, <, = operators which allow to use an index:
SELECT * FROM data
WHERE datetime BETWEEN '2009-10-20 00:00:00' AND '2009-10-20 23:59:59'
Update: the impact on using LIKE instead of operators in an indexed column is high. These are some test results on a table with 1,176,000 rows:
using datetime LIKE '2009-10-20%' => 2931ms
using datetime >= '2009-10-20 00:00:00' AND datetime <= '2009-10-20 23:59:59' => 168ms
When doing a second call over the same query the difference is even higher: 2984ms vs 7ms (yes, just 7 milliseconds!). I found this while rewriting some old code on a project using Hibernate.

Answer 3

You can format the datetime to the Y-M-D portion:
DATE_FORMAT(datetime, '%Y-%m-%d')

Answer 4

Though all the answers on the page will return the desired result, they all have performance issues. Never perform transformations on fields in the WHERE clause (including a DATE() calculation) as that transformation must be performed on all rows in the table.
The BETWEEN ... AND construct is inclusive for both border conditions, requiring one to specify the 23:59:59 syntax on the end date which itself has other issues (microsecond transactions, which I believe MySQL did not support in 2009 when the question was asked).
The proper way to query a MySQL timestamp field for a particular day is to check for Greater-Than-Equals against the desired date, and Less-Than for the day after, with no hour specified.
WHERE datetime>='2009-10-20' AND datetime<'2009-10-21'
This is the fastest-performing, lowest-memory, least-resource intensive method, and additionally supports all MySQL features and corner-cases such as sub-second timestamp precision. Additionally, it is future proof.

Answer 5

Here are all formats
Say this is the column that contains the datetime value, table data.
+--------------------+
| date_created |
+--------------------+
| 2018-06-02 15:50:30|
+--------------------+
mysql> select DATE(date_created) from data;
+--------------------+
| DATE(date_created) |
+--------------------+
| 2018-06-02 |
+--------------------+
mysql> select YEAR(date_created) from data;
+--------------------+
| YEAR(date_created) |
+--------------------+
| 2018 |
+--------------------+
mysql> select MONTH(date_created) from data;
+---------------------+
| MONTH(date_created) |
+---------------------+
| 6 |
+---------------------+
mysql> select DAY(date_created) from data;
+-------------------+
| DAY(date_created) |
+-------------------+
| 2 |
+-------------------+
mysql> select HOUR(date_created) from data;
+--------------------+
| HOUR(date_created) |
+--------------------+
| 15 |
+--------------------+
mysql> select MINUTE(date_created) from data;
+----------------------+
| MINUTE(date_created) |
+----------------------+
| 50 |
+----------------------+
mysql> select SECOND(date_created) from data;
+----------------------+
| SECOND(date_created) |
+----------------------+
| 31 |
+----------------------+

Answer 6

You can use:
DATEDIFF ( day , startdate , enddate ) = 0
Or:
DATEPART( day, startdate ) = DATEPART(day, enddate)
AND
DATEPART( month, startdate ) = DATEPART(month, enddate)
AND
DATEPART( year, startdate ) = DATEPART(year, enddate)
Or:
CONVERT(DATETIME,CONVERT(VARCHAR(12), startdate, 105)) = CONVERT(DATETIME,CONVERT(VARCHAR(12), enddate, 105))

Answer 7

simple and best way to use date function
example
SELECT * FROM
data
WHERE date(datetime) = '2009-10-20'
OR
SELECT * FROM
data
WHERE date(datetime ) >= '2009-10-20' && date(datetime ) <= '2009-10-20'

Answer 8

I tried date(tscreated) = '2022-06-04' on a large record set. My tscreated is indexed. It took 42 seconds.
I then tried tscreated >= '2022-06-04' and tscreated < '2022-06-05' and the time was .094 sec.
I realize that the record set might be in memory the second time, but I also believe that the date function negates the value of the index.

Answer 9

Well, using LIKE in statement is the best option
WHERE datetime LIKE '2009-10-20%'
it should work in this case