MySQL DATE_FORMAT函數(shù)簡介

要將日期值格式化為特定格式，請使用DATE_FORMAT函數(shù)。 DATE_FORMAT函數(shù)的語法如下：

DATE_FORMAT(date,format);

DATE_FORMAT()函數(shù)接受兩個參數(shù)：

• date：是要格式化的有效日期值
• format：是由預定義的說明符組成的格式字符串，每個說明符前面都有一個百分比字符(%)。有關(guān)預定義說明符的列表，請參見下表。

DATE_FORMAT函數(shù)返回字符集和校對規(guī)則取決于客戶端連接的設置的字符串。

下表說明了可用于構(gòu)建日期格式字符串的說明符及其含義：

以下是一些常用的日期格式字符串：

MySQL DATE_FORMAT示例

我們來看看示例數(shù)據(jù)庫中的orders表，其結(jié)果如下所示 -

mysql> desc orders;
+----------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra | 
+----------------+-------------+------+-----+---------+-------+
| orderNumber | int(11) | NO | PRI | NULL | |
| orderDate | date | NO | | NULL | |
| requiredDate | date | NO | | NULL | |
| shippedDate | date | YES | | NULL | |
| status | varchar(15) | NO | | NULL | |
| comments | text | YES | | NULL | |
| customerNumber | int(11) | NO | MUL | NULL | |
+----------------+-------------+------+-----+---------+-------+
7 rows in set

要選擇訂單的數(shù)據(jù)并格式化日期值，請使用以下語句：

SELECT
orderNumber,
DATE_FORMAT(orderdate, '%Y-%m-%d') orderDate,
DATE_FORMAT(requireddate, '%a %D %b %Y') requireddate,
DATE_FORMAT(shippedDate, '%W %D %M %Y') shippedDate
FROM
orders;

執(zhí)行上面查詢語句，得到以下結(jié)果 -

+-------------+------------+-------------------+------------------------------+
| orderNumber | orderDate | requireddate | shippedDate |
+-------------+------------+-------------------+------------------------------+
| 10100 | 2013-01-06 | Sun 13th Jan 2013 | Thursday 10th January 2013 |
| 10101 | 2013- 01-09 | Fri 18th Jan 2013 | Friday 11th January 2013 |
| 10102 | 2013-01-10 | Fri 18th Jan 2013 | Monday 14th January 2013 |
| 10103 | 2013- 01- 29 | Thu 7th Feb 2013 | Saturday 2nd February 2013
************* 此處省略了一大波數(shù)據(jù) *********************************
| 10417 | 2015- 05- 13 | Tue 19th May 2015 | Tuesday 19th May 2015 |
| 10418 | 2015-05-16 | Sun 24th May 2015 | Wednesday 20th May 2015 |
| 10419 | 2015- 05- 17 | Thu 28th May 2015 | Tuesday 19th May 2015
| 10425 | 2015- 05- 31 | Sun 7th Jun 2015 | NULL |
| 10426 | 2017-07-21 | Wed 26th Jul 2017 | Sunday 23rd July 2017 |
+-------------+------------+-------------------+------------------------------+
327 rows in set

要根據(jù)格式字符串指定的不同日期格式來格式化訂單日期，所需日期和每個訂單的發(fā)貨日期。

MySQL DATE_FORMAT與ORDER BY

請參閱以下示例：

SELECT
orderNumber,
DATE_FORMAT(shippeddate, '%W %D %M %Y') shippeddate
FROM
orders
WHERE
shippeddate IS NOT NULL
ORDER BY shippeddate;

執(zhí)行上面查詢語句，得到以下結(jié)果 -

+-------------+------------------------------+
| orderNumber | shippeddate |
+-------------+------------------------------+
| 10101 | Friday 11th January 2013 |
| 10156 | Friday 11th October 2013 |
| 10356 | Friday 12th December 2014 |
| 10376 | Friday 13th February 2015 |
| 10129 | Friday 14th June 2013 |
| 10279 | Friday 15th August 2014 |
| 10181 | Friday 15th November 2013 |
********* 此處省略了一大波數(shù)據(jù) ****************
| 10348 | Wednesday 5th November 2014 |
| 10411 | Wednesday 6th May 2015 |
| 10267 | Wednesday 9th July 2014 |
| 10300 | Wednesday 9th October 2013 |
+-------------+------------------------------+
313 rows in set

在查詢中，我們選擇了發(fā)貨日期不為NULL的所有訂單，并按發(fā)貨日期對訂單進行排序。但是，訂單未正確排序。

原因是將shippingdate用作DATE_FORMAT函數(shù)的輸出的別名，它是一個字符串，ORDER BY子句根據(jù)字符串值，而不是日期值對別名進行排序。

要解決這個問題，我們必須使用不同于列名的別名; 見下列聲明：

SELECT
orderNumber,
DATE_FORMAT(shippeddate, '%W %D %M %Y') 'Shipped date'
FROM
orders
WHERE
shippeddate IS NOT NULL
ORDER BY shippeddate;

執(zhí)行上面查詢語句，得到以下結(jié)果 -

+-------------+------------------------------+
| orderNumber | Shipped date |
+-------------+------------------------------+
| 10100 | Thursday 10th January 2013 |
| 10101 | Friday 11th January 2013 |
| 10102 | Monday 14th January 2013 |
| 10104 | Friday 1st February 2013 |
| 10103 | Saturday 2nd February 2013 |
| 10105 | Tuesday 12th February 2013 |
********* 此處省略了一大波數(shù)據(jù) ****************
| 10413 | Saturday 9th May 2015 |
| 10415 | Tuesday 12th May 2015 |
| 10416 | Thursday 14th May 2015 |
| 10417 | Tuesday 19th May 2015 |
| 10419 | Tuesday 19th May 2015 |
| 10418 | Wednesday 20th May 2015 |
| 10426 | Sunday 23rd July 2017 |
+-------------+------------------------------+
313 rows in set

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