MariaDB中MIN()的基本用法是什么 有哪些使用技巧吗

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MariaDB MIN()函数用于检索表达式的最小值。

语法：

SELECT MIN(aggregate_expression)

FROM tables

[WHERE conditions];

数据准备

在"testdb"数据库中创建一个"students"表，并插入一些数据。参考以下创建语句 -

USE testdb;

DROP TABLE students;

-- 创建新表

CREATE TABLE students(

student_id INT NOT NULL AUTO_INCREMENT,

student_name VARCHAR(100) NOT NULL,

student_address VARCHAR(40) default NULL,

admission_date DATE,

score float(4, 1) default NULL,

PRIMARY KEY ( student_id )

);

-- 插入数据

INSERT INTO students

(student_id, student_name, student_address,score, admission_date)

VALUES(1,'Maxsu','Haikou', 99.5,'2017-01-07 00:00:00');

INSERT INTO students

(student_id, student_name, student_address, score, admission_date)

VALUES

(2,'Crurry','Beijing',86,'2016-05-07 00:00:00'),

(3,'JMaster','Beijing',91,'2016-05-07 00:00:00'),

(4,'Mahesh','Guangzhou',78,'2016-06-07 00:00:00'),

(5,'Kobe','Shanghai',89,'2016-02-07 00:00:00'),

(6,'Blaba','Shengzhen',100,'2016-08-07 00:00:00');

1. MIN()函数与单表达式

示例：

查询Student表的最低分数。参考以下查询语句 -

SELECT Min(Score) AS "Lowest Score" FROM students;

执行上面查询语句，得到以下结果 -

MariaDB [testdb]> SELECT Min(Score) AS "Lowest Score" FROM students;

+--------------+

| Lowest Score |

+--------------+

| 78.0 |

+--------------+

1 row in set (0.00 sec)

2. Min()函数与GROUP BY子句

可以使用Min函数的GROUP BY子句来分组。

再插入一条重复的数据 -

INSERT INTO students

(student_name, student_address,score, admission_date)

VALUES('Maxsu','Haikou', 91,'2017-11-07 00:00:00');

当前数据库中的记录如下 -

MariaDB [testdb]> select * from students;

+------------+--------------+-----------------+----------------+-------+

| student_id | student_name | student_address | admission_date | score |

+------------+--------------+-----------------+----------------+-------+

| 1 | Maxsu | Haikou | 2017-01-07 | 99.5 |

| 2 | Crurry | Beijing | 2016-05-07 | 86.0 |

| 3 | JMaster | Beijing | 2016-05-07 | 91.0 |

| 4 | Mahesh | Guangzhou | 2016-06-07 | 78.0 |

| 5 | Kobe | Shanghai | 2016-02-07 | 89.0 |

| 6 | Blaba | Shengzhen | 2016-08-07 | 100.0 |

| 7 | Maxsu | Haikou | 2017-11-07 | 91.0 |

+------------+--------------+-----------------+----------------+-------+

7 rows in set (0.07 sec)

示例：

SELECT student_name, MIN(score) AS "Lowest Score"

FROM Students

where student_id < 10

GROUP BY student_name;

执行上面查询语句，得到以下结果 -

MariaDB [testdb]> SELECT student_name, MIN(score) AS "Lowest Score"

-> FROM Students

-> where student_id < 10

-> GROUP BY student_name;

+--------------+--------------+

| student_name | Lowest Score |

+--------------+--------------+

| Blaba | 100.0 |

| Crurry | 86.0 |

| JMaster | 91.0 |

| Kobe | 89.0 |

| Mahesh | 78.0 |

| Maxsu | 91.0 |

+--------------+--------------+

6 rows in set (0.00 sec)

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