Mysql中提供了STR_TO_DATE()函數(shù)，可以將字符串轉(zhuǎn)換成日期格式。此函數(shù)的用法如下：

STR_TO_DATE(str, format)

其中，str表示待轉(zhuǎn)換的字符串，format表示格式化日期的規(guī)則。常見的日期格式化規(guī)則如下：

'%%' ->'%'
'%a' ->Abbreviated weekday name (Sun..Sat)
'%b' ->Abbreviated month name (Jan..Dec)
'%c' ->Month, numeric (0..12)
'%D' ->Day of the month with English suffix (0th, 1st, 2nd, 3rd, …)
'%d' ->Day of the month, numeric (00..31)
'%e' ->Day of the month, numeric (0..31)
'%f' ->Microseconds (000000..999999)
'%H' ->Hour (00..23)
'%h' ->Hour (00..12)
'%I' ->Hour (01..12)
'%i' ->Minutes, numeric (00..59)
'%j' ->Day of year (001..366)
'%k' ->Hour (0..23)
'%l' ->Hour (1..12)
'%M' ->Month name (January..December)
'%m' ->Month, numeric (00..12)
'%p' ->AM or PM
'%r' ->Time, 12-hour (hh:mm:ss followed by AM or PM)
'%S' ->Seconds (00..59)
'%s' ->Seconds (00..59)
'%T' ->Time, 24-hour (hh:mm:ss)
'%U' ->Week (0..52), where Sunday is the first day of the week
'%u' ->Week (0..52), where Monday is the first day of the week
'%V' ->Week (1..53), where Sunday is the first day of the week; used with %X
'%v' ->Week (1..53), where Monday is the first day of the week; used with %x
'%W' ->Weekday name (Sunday..Saturday)
'%w' ->Day of the week (0=Sunday..6=Saturday)
'%X' ->Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V
'%x' ->Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v
'%Y' ->Year, numeric, four digits
'%y' ->Year, numeric (two digits)

舉個例子，假設有如下數(shù)據(jù)表student：姓名、年齡、出生日期（字符串類型）。可以使用如下sql語句將出生日期改為日期類型：

UPDATE student SET birthdate = STR_TO_DATE(birthdate,'%Y-%m-%d');