floor(x) 返回小於x的最大整數值
mysql> select * from t13; +------+--------+----------+ | id | name | fraction | +------+--------+----------+ | 1 | 李四 | 65.5 | +------+--------+----------+ 1 row in set (0.00 sec) mysql> select fraction from t13; +----------+ | fraction | +----------+ | 65.5 | +----------+ 1 row in set (0.00 sec)
#floor截取fraction值的整數部分.
mysql> select floor(fraction) from t13; +-----------------+ | floor(fraction) | +-----------------+ | 65 | +-----------------+ 1 row in set (0.00 sec)
rand()：返回0到1之間的隨機數.
mysql> select rand(); +-------------------+ | rand() | +-------------------+ | 0.874798723379894 | +-------------------+ 1 row in set (0.00 sec)
返回5-10之間的隨機數.
mysql> select rand()*5+5; +-------------------+ | rand()*5+5 | +-------------------+ | 6.166499062596354 | +-------------------+ 1 row in set (0.00 sec)
mysql> select rand()*5+5; +-------------------+ | rand()*5+5 | +-------------------+ | 7.710514615951585 | +-------------------+ 1 row in set (0.00 sec)
配合floor可以得到5-10之間的隨機整數.
mysql> select floor(rand()*5+5); +-------------------+ | floor(rand()*5+5) | +-------------------+ | 5 | +-------------------+ 1 row in set (0.00 sec)
mysql> select floor(rand()*5+5); +-------------------+ | floor(rand()*5+5) | +-------------------+ | 7 | +-------------------+ 1 row in set (0.00 sec)
position獲取指定字符串所在列的位置,從1開始計數.
mysql> create table t18 (
-> email char(20)
-> );
Query OK, 0 rows affected (0.02 sec)
mysql> insert into t18 values ("[email protected]"),("[email protected]");
Query OK, 2 rows affected (0.02 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from t18;
+---------------+
| email |
+---------------+
| [email protected] |
| [email protected] |
+---------------+
2 rows in set (0.00 sec)position使用的語法:
mysql> select position('@' in email) from t18;
+------------------------+
| position('@' in email) |
+------------------------+
| 4 |
| 6 |
+------------------------+
2 rows in set (0.00 sec)left語法截取:
mysql> select left(email,position('@' in email)) from t18;
+------------------------------------+
| left(email,position('@' in email)) |
+------------------------------------+
| abc@ |
| 12356@ |
+------------------------------------+
2 rows in set (0.01 sec)mysql> select left(email,position('@' in email)-1) from t18;
+--------------------------------------+
| left(email,position('@' in email)-1) |
+--------------------------------------+
| abc |
| 12356 |
+--------------------------------------+
2 rows in set (0.00 sec)date_format:時間戳函數.
mysql> select now(); +---------------------+ | now() | +---------------------+ | 2019-02-15 23:09:31 | +---------------------+ 1 row in set (0.00 sec) mysql> select date_format(now(),'%Y%m'); +---------------------------+ | date_format(now(),'%Y%m') | +---------------------------+ | 201902 | +---------------------------+ 1 row in set (0.00 sec) mysql> select date_format(now(),'%Y%m%d'); +-----------------------------+ | date_format(now(),'%Y%m%d') | +-----------------------------+ | 20190215 | +-----------------------------+ 1 row in set (0.00 sec)