Mysql 常用函数汇总

☆日期函数

日期符号对应关系

年	月	日	时	分	秒
Y	m	d	H	i	s

获取当前日期 now()

> select now();+---------------------+| now()               |+---------------------+| 2020-06-02 22:21:20 |+---------------------+1 row in set (0.03 sec)

获取当前时间戳 current_timestamp

> select current_timestamp, current_timestamp();+---------------------+---------------------+| current_timestamp   | current_timestamp() |+---------------------+---------------------+| 2020-06-02 22:23:27 | 2020-06-02 22:23:27 |+---------------------+---------------------+

格式转换: 时间->字符串 date_format

> select date_format('2020-10-18 22:23:01', '%Y-%m-%d %H%i%s');+-------------------------------------------------------+| date_format('2020-10-18 22:23:01', '%Y-%m-%d %H%i%s') |+-------------------------------------------------------+| 2020-10-18 222301                                     |+-------------------------------------------------------+

格式转换: 字符串->时间 str_to_date

> select str_to_date('08/09/2008', '%m/%d/%Y');+---------------------------------------+| str_to_date('08/09/2008', '%m/%d/%Y') |+---------------------------------------+| 2008-08-09                            |+---------------------------------------+1 row in set (0.03 sec)

星期几DAYOFWEEK

周日1，周一2...周六7

> select now(), dayofweek(now());+---------------------+------------------+| now()               | dayofweek(now()) |+---------------------+------------------+| 2020-06-03 21:48:03 |                4 |

获取年月日时分秒周

> select now(), dayofweek(now()), year(now()), month(now()), day(now()), hour(now()), minute(now()), second(now()),week(now());+---------------------+------------------+-------------+--------------+------------+-------------+---------------+---------------+-------------+| now()               | dayofweek(now()) | year(now()) | month(now()) | day(now()) | hour(now()) | minute(now()) | second(now()) | week(now()) |+---------------------+------------------+-------------+--------------+------------+-------------+---------------+---------------+-------------+| 2020-06-03 21:50:13 |                4 |        2020 |            6 |          3 |          21 |            50 |            13 |          22 |

☆字符串处理

字符串拼接 concat

将多个字符串连接成一个字符串

> select concat('2020', '/', '12', '/', '20');+--------------------------------------+| concat('2020', '/', '12', '/', '20') |+--------------------------------------+| 2020/12/20                           |+--------------------------------------+

以第一个字符为拼接符：concat_ws

> select concat_ws('/', '2020', '12', '20');+------------------------------------+| concat_ws('/', '2020', '12', '20') |+------------------------------------+| 2020/12/20                         |+------------------------------------+

字符串截取：left, right, substring

> select left('123456', 3), right('123456', 3), left('123', 100);+-------------------+--------------------+------------------+| left('123456', 3) | right('123456', 3) | left('123', 100) |+-------------------+--------------------+------------------+| 123               | 456                | 123              |+-------------------+--------------------+------------------+

substring

用法：substring(字符串, 位置, 长度)

> select substring('123456', 3);   # 从第3个开始截取+------------------------+| substring('123456', 3) |+------------------------+| 3456                   |+------------------------+1 row in set (0.03 sec)> select substring('123456', 3, 2);   #从第三个开始，只截2个+---------------------------+| substring('123456', 3, 2) |+---------------------------+| 34                        |+---------------------------+1 row in set (0.03 sec)> select substring('123456', -3);   #从倒数第3个开始+-------------------------+| substring('123456', -3) |+-------------------------+| 456                     |+-------------------------+1 row in set (0.03 sec)> select substring('123456', -3, 2);  # 从倒数第3个开始，只截2个+----------------------------+| substring('123456', -3, 2) |+----------------------------+| 45                         |+----------------------------+1 row in set (0.03 sec)> select substring('123456', -3, -2);  # 第三个参数是长度，为正有意义+-----------------------------+| substring('123456', -3, -2) |+-----------------------------+|                             |+-----------------------------+

按关键字截取 substring_index

用法substring_index(str, delim, count)，即：substring_index(被截取字符串，关键字，关键字出现的次数)

> select substring_index('123aaa3bb3dd', '3', 1);+-----------------------------------------+| substring_index('123aaa3bb3dd', '3', 1) |+-----------------------------------------+| 12                                      |+-----------------------------------------+> select substring_index('123aaa3bb3dd', '3', 2);+-----------------------------------------+| substring_index('123aaa3bb3dd', '3', 2) |+-----------------------------------------+| 123aaa                                  |+-----------------------------------------+

最左边字符的ascii码

>select ASCII(2), ASCII('2'), ASCII('22');+----------+------------+-------------+| ASCII(2) | ASCII('2') | ASCII('22') |+----------+------------+-------------+|       50 |         50 |          50 |

字符串长度 LENGHT

>select length('abc'), length(333333);+---------------+----------------+| length('abc') | length(333333) |+---------------+----------------+|             3 |              6 |

一字符串在另一个字符串中的位置 locate(substr, str), instr(str, substr)

返回substr在str出现的第一个位置，如果在则>0；否则为0

> select locate('abc', 'mmabcmm'), locate('abc', 'aaaaaa');+--------------------------+-------------------------+| locate('abc', 'mmabcmm') | locate('abc', 'aaaaaa') |+--------------------------+-------------------------+|                        3 |                       0 |+--------------------------+-------------------------+> select instr('abc', 'a'), locate('abc', 'aa');+-------------------+---------------------+| instr('abc', 'a') | locate('abc', 'aa') |+-------------------+---------------------+|                 1 |                   0 |+-------------------+---------------------+

替换REPLACE

> select replace('www.baidu.com.ww', 'ww', '&&');+-----------------------------------------+| replace('www.baidu.com.ww', 'ww', '&&') |+-----------------------------------------+| &&w.baidu.com.&&                        |

指定位置字符替换

insert(con, pos, len, anotherstr), 把字符con, 从第pos(从1开始计数)的len个字符由anotherstr替换

> select insert('123456', 3, 3, 'aaaaa');+---------------------------------+| insert('123456', 3, 3, 'aaaaa') |+---------------------------------+| 12aaaaa6                        |

重复REPEAT

> select repeat('abc', 3);+------------------+| repeat('abc', 3) |+------------------+| abcabcabc        |

翻转REVERSE

> select reverse('abc');+----------------+| reverse('abc') |+----------------+| cba            |

☆数学函数

绝对值ABS, 取余MOD

> select abs(-3.2), mod(3, 4);+-----------+-----------+| abs(-3.2) | mod(3, 4) |+-----------+-----------+|       3.2 |         3 |+-----------+-----------+

四舍五入 ROUND

select round(1.49), round(1.50);+-------------+-------------+| round(1.49) | round(1.50) |+-------------+-------------+|           1 |           2 |+-------------+-------------+

不大于x的最大整数FLOOR，不小于x的最小整数CEILING

> select FLOOR(-1.23), FLOOR(1.23), CEILING(-1.23), CEILING(1.23);+--------------+-------------+----------------+---------------+| FLOOR(-1.23) | FLOOR(1.23) | CEILING(-1.23) | CEILING(1.23) |+--------------+-------------+----------------+---------------+|           -2 |           1 |             -1 |             2 |

☆控制流程函数

条件控制 case when then

> select case when 1 < 0 then 'a' when 2 > 1 then 'b' else 'c' end;+-----------------------------------------------------------+| case when 1 < 0 then 'a' when 2 > 1 then 'b' else 'c' end |+-----------------------------------------------------------+| b                                                         |

☆加密函数

password 一般对用户密码加密

> select password('a');+-------------------------------------------+| password('a')                             |+-------------------------------------------+| *667F407DE7C6AD07358FA38DAED7828A72014B4E |

md5一般对普通数据加密

> select md5('abc');+----------------------------------+| md5('abc')                       |+----------------------------------+| 900150983cd24fb0d6963f7d28e17f72 |

加密ENCODE, 解密DECODE

encode(str, pwd_str), decode(str, pwd_str), 使用pwd_str对str进行加密、解密

select encode('abc', '123'), decode(encode('abc', '123'), '123');+----------------------+-------------------------------------+| encode('abc', '123') | decode(encode('abc', '123'), '123') |+----------------------+-------------------------------------+| ���                  | abc                                 |

文章转载于:https://www.cnblogs.com/kaituorensheng/p/13034500.html

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