1日期函数
mysql> select current_date() from dual;
mysql> select current_time() from dual;
mysql> select month(current_date()) from dual;
mysql> select year(current_date()) from dual;
mysql> select month(current_date()) from dual;
mysql> select day(current_date()) from dual;
mysql> select hour(current_time()) from dual;
mysql> select minute(current_time()) from dual;
mysql> select second(current_time()) from dual;
create table message (
id int,
title varchar(64),
publishdate datetime
);
mysql> insert into message (id,title,publishdate)values(1,'abc',now());
Query OK, 1 row affected (0.09 sec)
mysql> insert into message (id,title,publishdate)values(1,'efc','2011-1-1');
Query OK, 1 row affected (0.09 sec)
备注：插入时间的内容可以是字符串，但是必须是日期格式
查询最近两个小时的内容
select * from message where date_add(publishdate,interval 2 hour)>= now();
选择了最近的 30天内所有带有date_col 值的记录：
mysql> SELECT something FROM tbl_name
-> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col;
函数调用格式
DATE_ADD(date,INTERVAL expr type)
DATE_SUB(date,INTERVAL expr type)
| type值 |
预期的 expr格式 |
| MICROSECOND |
MICROSECONDS |
| SECOND |
SECONDS |
| MINUTE |
MINUTES |
| HOUR |
HOURS |
| DAY |
DAYS |
| WEEK |
WEEKS |
| MONTH |
MONTHS |
| QUARTER |
QUARTERS |
| YEAR |
YEARS |
2字符串函数
mysql> select * from employee;
+------+------+------+------------+--------+------------+------------+
| id | name | sex | birthday | salary | entry_date | resume |
+------+------+------+------------+--------+------------+------------+
| 1 | aaa | | 1977-11-11 | 56.8 | 2014-11-10 | hello word |
| 2 | bbb | | 1977-11-11 | 57.8 | 2014-11-10 | hello word |
| 3 | ccc | | 1977-11-11 | 56.3 | 2014-11-10 | hello word |
+------+------+------+------------+--------+------------+------------+
1rows in set (0.00 sec)
名字首字母大写
select SUBSTRING(UCASE(name),1,1) from employee;
select SUBSTRING(LCASE(name),2,LENGTH(name)-1) from employee;
select CONCAT(SUBSTRING(UCASE(name),1,1), SUBSTRING(LCASE(name),2,LENGTH(name)-1)) from employee;
备注：SUBSTRING从第一个数从0开始
3数学函数
4加密函数
4.1md5加密
mysql> select md5('huangbiao') from dual;
+----------------------------------+
| md5('huangbiao') |
+----------------------------------+
| 1d7877a910293815774015e3776afa0c |
+----------------------------------+
1 row in set (0.00 sec)
mysql> select md5('huangbiao') ;
+----------------------------------+
| md5('huangbiao') |
+----------------------------------+
| 1d7877a910293815774015e3776afa0c |
+----------------------------------+
4.2password(str)
从原文密码str 计算并返回密码字符串，当参数为 NULL 时返回 NULL。这个函数用于用户授权表的Password列中的加密MySQL密码存储
mysql> select password('1');
+-------------------------------------------+
| password('1') |
+-------------------------------------------+
| *E6CC90B878B948C35E92B003C792C46C58C4AF40 |
+-------------------------------------------+
mysql> select password(NULL);
+----------------+
| password(NULL) |
+----------------+
| NULL |
+----------------+
4.3SHA1(str) SHA(str)
mysql> SELECT SHA1('1');
+------------------------------------------+
| SHA1('1') |
+------------------------------------------+
| 356a192b7913b04c54574d18c28d46e6395428ab |
+------------------------------------------+
1 row in set (0.00 sec)
mysql> SELECT SHA('1');
+------------------------------------------+
| SHA('1') |
+------------------------------------------+
| 356a192b7913b04c54574d18c28d46e6395428ab |
+------------------------------------------+
1 row in set (0.00 sec)
4.4DECODE(crypt_str,pass_str) 和 ENCODE(str,pass_str)
使用 pass_str 作为密码，解密加密字符串 crypt_str， crypt_str 应该是由ENCODE()返回的字符串。
使用pass_str 作为密码，解密 str 。 使用DECODE()解密结果