SQL中常用的文本处理函数和日期时间处理函数
常用文本处理函数
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CONCAT(str1, str2, ...)：拼接字符串mysql> SELECT CONCAT('There', ' is', ' an', ' apple.'); +------------------------------------------+ | CONCAT('There', ' is', ' an', ' apple.') | +------------------------------------------+ | There is an apple. | +------------------------------------------+ -
CONCAT_WS(separator, str1, str2, ...)：使用指定分隔符连接字符串mysql> SELECT CONCAT_WS('-', 'There', 'is', 'an', 'apple'); +----------------------------------------------+ | CONCAT_WS('-', 'There', 'is', 'an', 'apple') | +----------------------------------------------+ | There-is-an-apple | +----------------------------------------------+ -
LEFT(str, length)：从左截取指定长度的子字符串mysql> SELECT LEFT('ZHANG SAN', 5); +----------------------+ | LEFT('ZHANG SAN', 5) | +----------------------+ | ZHANG | +----------------------+ -
RIGHT(str, length)：从右截取指定长度的子字符串mysql> SELECT RIGHT('ZHANG SAN', 3); +-----------------------+ | RIGHT('ZHANG SAN', 3) | +-----------------------+ | SAN | +-----------------------+ -
SUBSTRING(str, index, length)：从指定位置处开始截取指定长度的子字符串mysql> SELECT SUBSTRING('ABCDEFG', 3, 4); +----------------------------+ | SUBSTRING('ABCDEFG', 3, 4) | +----------------------------+ | CDEF | +----------------------------+ -
LENGTH(str)：返回字符串的长度mysql> SELECT LENGTH('ZHANG SAN'); +---------------------+ | LENGTH('ZHANG SAN') | +---------------------+ | 9 | +---------------------+ -
LOWER(str)：将字符串转换为小写格式mysql> SELECT LOWER('ZHANG SAN'); +--------------------+ | LOWER('ZHANG SAN') | +--------------------+ | zhang san | +--------------------+ -
UPPER(str)：将字符串转换为大写格式mysql> SELECT UPPER('zhang san'); +--------------------+ | UPPER('zhang san') | +--------------------+ | ZHANG SAN | +--------------------+ -
LTRIM(str)：去除字符串左侧的空格mysql> SELECT CONCAT('(', LTRIM(' LEFT'), ')'); +------------------------------------+ | CONCAT('(', LTRIM(' LEFT'), ')') | +------------------------------------+ | (LEFT) | +------------------------------------+ -
RTRIM(str)：去除字符串右侧的空格mysql> SELECT CONCAT('(', RTRIM('RIGHT '), ')'); +-------------------------------------+ | CONCAT('(', RTRIM('RIGHT '), ')') | +-------------------------------------+ | (RIGHT) | +-------------------------------------+ -
TRIM(str)：去除字符串两侧的空格mysql> SELECT CONCAT('(', TRIM(' MIDDLE '), ')'); +----------------------------------------+ | CONCAT('(', TRIM(' MIDDLE '), ')') | +----------------------------------------+ | (MIDDLE) | +----------------------------------------+ -
ELT(index, str1, str2, ...)：返回字符串序列中指定位置的字符串mysql> SELECT ELT(3, 'A', 'B', 'C', 'D'); +----------------------------+ | ELT(3, 'A', 'B', 'C', 'D') | +----------------------------+ | C | +----------------------------+ -
FIELD(str, str1, str2, ...)：返回指定字符串str在字符串序列中的位置，找不到返回0mysql> SELECT FIELD('C', 'A', 'B', 'C', 'D'); +--------------------------------+ | FIELD('C', 'A', 'B', 'C', 'D') | +--------------------------------+ | 3 | +--------------------------------+ -
FIND_IN_SET(str, stringList)：返回指定字符串str在由“,”分割的字符串序列中的位置mysql> SELECT FIND_IN_SET('C', 'A,B,C,D'); +-----------------------------+ | FIND_IN_SET('C', 'A,B,C,D') | +-----------------------------+ | 3 | +-----------------------------+ -
FORMAT(X, D)：按照指定的小数位数D将数值X转化为字符串mysql> SELECT FORMAT(123.45678, 2); +----------------------+ | FORMAT(123.45678, 2) | +----------------------+ | 123.46 | +----------------------+ -
INSERT(str, index, length, newString)：从指定位置开始用新字符串替换原字符串中指定长度的字符，index超出原字符串范围时返回原字符串mysql> SELECT INSERT('ABCDEF', 3, 3, '123'); +-------------------------------+ | INSERT('ABCDEF', 3, 3, '123') | +-------------------------------+ | AB123F | +-------------------------------+ -
LOCATE(substr, str)：返回子字符串在指定字符串中第一次出现的位置LOCATE(substr, str, index)：从指定字符串的指定位置处开始查找子字符串出现的位置找不到返回0
mysql> SELECT LOCATE('a', 'banana'); +-----------------------+ | LOCATE('a', 'banana') | +-----------------------+ | 2 | +-----------------------+ mysql> SELECT LOCATE('a', 'banana', 3); +--------------------------+ | LOCATE('a', 'banana', 3) | +--------------------------+ | 4 | +--------------------------+ -
LPAD(str, length, padStr)：在字符串左侧用padStr将原字符串填充至指定长度，当指定长度小于原字符串长度时，截断原字符串mysql> SELECT LPAD('HELLO', 8, '!'); +-----------------------+ | LPAD('HELLO', 8, '!') | +-----------------------+ | !!!HELLO | +-----------------------+ -
RPAD(str, length, padStr)：在字符串右侧用padStr将原字符串填充至指定长度，当指定长度小于原字符串长度时，截断原字符串mysql> SELECT RPAD('HELLO', 8, '!'); +-----------------------+ | RPAD('HELLO', 8, '!') | +-----------------------+ | HELLO!!! | +-----------------------+ -
REPEAT(str, times)：按照指定次数重复字符串mysql> SELECT REPEAT('LA', 3); +-----------------+ | REPEAT('LA', 3) | +-----------------+ | LALALA | +-----------------+ -
REPLACE(str, from_str, to_str)：将字符串中的所有匹配的字符串替换为新字符串mysql> SELECT REPLACE('LALALA', 'L', 'B'); +-----------------------------+ | REPLACE('LALALA', 'L', 'B') | +-----------------------------+ | BABABA | +-----------------------------+ -
REVERSE(str)：将字符串逆序输出mysql> SELECT REVERSE('ABC'); +----------------+ | REVERSE('ABC') | +----------------+ | CBA | +----------------+
常用日期和时间处理函数
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NOW()：返回当前的时间和日期mysql> SELECT NOW(); +---------------------+ | NOW() | +---------------------+ | 2019-03-25 18:01:47 | +---------------------+ -
CURDATE()：返回当前的日期mysql> SELECT CURDATE(); +------------+ | CURDATE() | +------------+ | 2019-03-25 | +------------+ -
CURTIME()：返回当前时间mysql> SELECT CURTIME(); +-----------+ | CURTIME() | +-----------+ | 18:05:02 | +-----------+ -
DATE(dateAndTime)：提取日期时间表达式中的日期部分mysql> SELECT DATE(NOW()); +-------------+ | DATE(NOW()) | +-------------+ | 2019-03-25 | +-------------+ -
DAY()：返回日期时间表达式中的天数部分mysql> SELECT DAY(NOW()); +------------+ | DAY(NOW()) | +------------+ | 25 | +------------+ -
YEAR()：返回日期时间表达式中的年部分mysql> SELECT YEAR(NOW()); +-------------+ | YEAR(NOW()) | +-------------+ | 2019 | +-------------+ -
EXTRACT(unit FROM date)：按照指定的时间单位从日期时间表达式中提取年、月、日、时间等部分mysql> SELECT EXTRACT(YEAR FROM NOW()); +--------------------------+ | EXTRACT(YEAR FROM NOW()) | +--------------------------+ | 2019 | +--------------------------+ mysql> SELECT EXTRACT(WEEK FROM NOW()); +--------------------------+ | EXTRACT(WEEK FROM NOW()) | +--------------------------+ | 12 | +--------------------------+ mysql> SELECT EXTRACT(HOUR_MICROSECOND FROM NOW()); +--------------------------------------+ | EXTRACT(HOUR_MICROSECOND FROM NOW()) | +--------------------------------------+ | 191218000000 | +--------------------------------------+时间单位的值可参考Temporal Intervals文档
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DATE_FORMAT(date, format)：按照指定格式显示时间日期可选的格式可参考Date and time functions
mysql> SELECT DATE_FORMAT(NOW(), '%W %M %Y'); +--------------------------------+ | DATE_FORMAT(NOW(), '%W %M %Y') | +--------------------------------+ | Monday March 2019 | +--------------------------------+ -
DATE_ADD(date, INTERVAL exp unit)、DATE_SUB(date, INTERVAL exp unit)：日期和时间的加减操作。返回值是否包含时间取决于给定的时间日期的表达式和时间单位。mysql> SELECT DATE_ADD('2018-03-25', INTERVAL 1 DAY); +----------------------------------------+ | DATE_ADD('2018-03-25', INTERVAL 1 DAY) | +----------------------------------------+ | 2018-03-26 | +----------------------------------------+ mysql> SELECT DATE_SUB('2018-03-25 19:26:47', INTERVAL 1 HOUR); +--------------------------------------------------+ | DATE_SUB('2018-03-25 19:26:47', INTERVAL 1 HOUR) | +--------------------------------------------------+ | 2018-03-25 18:26:47 | +--------------------------------------------------+ -
DATEDIFF(date1, date2)：返回两个日期的差值，会忽略表达式中的时间，仅对日期进行运算mysql> SELECT DATEDIFF('2018-4-30', NOW()); +------------------------------+ | DATEDIFF('2018-4-30', NOW()) | +------------------------------+ | -329 | +------------------------------+ 1 row in set (0.00 sec) -
ADDDATE(date, INTERVAL exp unit)：等同于DATE_ADD()ADDDATE(date, days)：在给定的日期上加上给定的天数mysql> SELECT ADDDATE(NOW(), 31); +---------------------+ | ADDDATE(NOW(), 31) | +---------------------+ | 2019-04-25 19:39:53 | +---------------------+ -
ADDTIME(time1, time2)：将两个时间表达式相加mysql> SELECT ADDTIME('10:33:24', '22:23:22'); +---------------------------------+ | ADDTIME('10:33:24', '22:23:22') | +---------------------------------+ | 32:56:46 | +---------------------------------+