轉(zhuǎn)載自? ?MySQL datediff()函數(shù)

MySQL DATEDIFF函數(shù)介紹

MySQL?DATEDIFF函數(shù)計(jì)算兩個(gè)DATE，DATETIME或TIMESTAMP值之間的天數(shù)。

MySQL?DATEDIFF函數(shù)的語(yǔ)法如下：

DATEDIFF(date_expression_1,date_expression_2);

DATEDIFF函數(shù)接受兩個(gè)任何有效日期或日期時(shí)間值的參數(shù)。如果您傳遞DATETIME或TIMESTAMP值，則DATEDIFF函數(shù)僅將日期部分用于計(jì)算，并忽略時(shí)間部分。

DATEDIFF函數(shù)在許多情況下很有用，例如，您可以計(jì)算產(chǎn)品需要發(fā)送給客戶(hù)的間隔時(shí)間。

MySQL DATEDIFF示例

我們來(lái)看一下使用DATEDIFF函數(shù)的一些例子。

示例-1

mysql> SELECT DATEDIFF('2017-08-17','2017-08-17'); +-------------------------------------+ | DATEDIFF('2017-08-17','2017-08-17') | +-------------------------------------+ | 0 | +-------------------------------------+ 1 row in set

示例-2

mysql> SELECT DATEDIFF('2017-08-17','2017-08-08'); +-------------------------------------+ | DATEDIFF('2017-08-17','2017-08-08') | +-------------------------------------+ | 9 | +-------------------------------------+ 1 row in set

示例-3

mysql> SELECT DATEDIFF('2017-08-08','2017-08-17'); +-------------------------------------+ | DATEDIFF('2017-08-08','2017-08-17') | +-------------------------------------+ | -9 | +-------------------------------------+ 1 row in set

請(qǐng)參閱示例數(shù)據(jù)庫(kù)(yiibaidb)中的以下orders表，其結(jié)構(gòu)如下 -

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

假設(shè)使用DATEDIFF函數(shù)計(jì)算所需日期和訂單發(fā)貨日期之間的天數(shù)，如下所示：

SELECT orderNumber, DATEDIFF(requiredDate, shippedDate) daysLeft FROMorders ORDER BY daysLeft DESC;

執(zhí)行上面查詢(xún)語(yǔ)句，得到以下結(jié)果 -

+-------------+----------+ | orderNumber | daysLeft | +-------------+----------+ | 10409 | 11 | | 10410 | 10 | | 10105 | 9 | | 10135 | 9 | | 10190 | 9 | **** 此處省略了一大小波數(shù)據(jù) ******** | 10423 | NULL | | 10424 | NULL | | 10425 | NULL | +-------------+----------+ 327 rows in set

以下語(yǔ)句將獲取狀態(tài)正在處理(In Process)的所有訂單，并計(jì)算訂單日期和所需日期之間的天數(shù)：

SELECT orderNumber,DATEDIFF(requiredDate, orderDate) remaining_days FROMorders WHEREstatus = 'In Process' ORDER BY remaining_days;

執(zhí)行上面查詢(xún)語(yǔ)句，得到以下結(jié)果 -

+-------------+----------------+ | orderNumber | remaining_days | +-------------+----------------+ | 10426 | 5 | | 10423 | 6 | | 10425 | 7 | | 10421 | 8 | | 10424 | 8 | | 10420 | 9 | | 10422 | 12 | +-------------+----------------+ 7 rows in set

要計(jì)算周或月作為間隔時(shí)間，可以將DATEDIFF函數(shù)的返回值除以7或30，如下查詢(xún)語(yǔ)句：

SELECT orderNumber,ROUND(DATEDIFF(requiredDate, orderDate) / 7, 2) as weeks,ROUND(DATEDIFF(requiredDate, orderDate) / 30,2) as months FROMorders WHEREstatus = 'In Process';

執(zhí)行上面查詢(xún)語(yǔ)句，得到以下結(jié)果 -

+-------------+-------+--------+ | orderNumber | weeks | months | +-------------+-------+--------+ | 10420 | 1.29 | 0.3 | | 10421 | 1.14 | 0.27 | | 10422 | 1.71 | 0.4 | | 10423 | 0.86 | 0.2 | | 10424 | 1.14 | 0.27 | | 10425 | 1 | 0.23 | | 10426 | 0.71 | 0.17 | +-------------+-------+--------+ 7 rows in set

請(qǐng)注意，ROUND函數(shù)用于舍入結(jié)果。

在本教程中，您已經(jīng)學(xué)習(xí)了如何使用MySQL?DATEDIFF函數(shù)來(lái)計(jì)算兩個(gè)日期值之間的天數(shù)。

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