Python Data Access 简明教程
Python MySQL - Order By
在使用 SELECT 查询获取数据时， يمكنك使用 OrderBy 子句以所需的順序（升序或降序）对结果进行排序。默认情况下，此子句按升序对结果进行排序，如果你需要按降序排列结果，则需要明确使用“DESC”。
Syntax
以下是 SELECT column-list 的语法
FROM table_name
[WHERE condition]
[ORDER BY column1, column2,.. columnN] [ASC | DESC]; of the ORDER BY clause:Example
假设我们在 MySQL 中使用 EMPLOYEES 作为名称创建了一个表格，如下所示：
mysql> CREATE TABLE EMPLOYEE(
FIRST_NAME CHAR(20) NOT NULL,
LAST_NAME CHAR(20),
AGE INT,
SEX CHAR(1),
INCOME FLOAT
);
Query OK, 0 rows affected (0.36 sec)如果使用 INSERT 语句向其中插入了 4 条记录，如下所示：
mysql> INSERT INTO EMPLOYEE VALUES
('Krishna', 'Sharma', 19, 'M', 2000),
('Raj', 'Kandukuri', 20, 'M', 7000),
('Ramya', 'Ramapriya', 25, 'F', 5000),
('Mac', 'Mohan', 26, 'M', 2000);以下语句按升序检索 EMPLOYEE 表的内容。
mysql> SELECT * FROM EMPLOYEE ORDER BY AGE;
+------------+-----------+------+------+--------+
| FIRST_NAME | LAST_NAME | AGE | SEX | INCOME |
+------------+-----------+------+------+--------+
| Krishna | Sharma | 19 | M | 2000 |
| Raj | Kandukuri | 20 | M | 7000 |
| Ramya | Ramapriya | 25 | F | 5000 |
| Mac | Mohan | 26 | M | 2000 |
+------------+-----------+------+------+--------+
4 rows in set (0.04 sec)你还可以使用 DESC 按降序检索数据，如下所示：
mysql> SELECT * FROM EMPLOYEE ORDER BY FIRST_NAME, INCOME DESC;
+------------+-----------+------+------+--------+
| FIRST_NAME | LAST_NAME | AGE | SEX | INCOME |
+------------+-----------+------+------+--------+
| Krishna | Sharma | 19 | M | 2000 |
| Mac | Mohan | 26 | M | 2000 |
| Raj | Kandukuri | 20 | M | 7000 |
| Ramya | Ramapriya | 25 | F | 5000 |
+------------+-----------+------+------+--------+
4 rows in set (0.00 sec)ORDER BY clause using python
要按特定顺序检索表的某个内容，调用游标对象上的 execute() 方法，并将 SELECT 语句和 ORDER BY 子句作为参数传递给它。
Example
在以下示例中，我们使用 ORDER BY 子句创建了一个名为 Employee 的表，对其进行填充，然后按其年龄的（升序）顺序检索其记录。
import mysql.connector
#establishing the connection
conn = mysql.connector.connect(
user='root', password='password', host='127.0.0.1', database='mydb')
#Creating a cursor object using the cursor() method
cursor = conn.cursor()
#Doping EMPLOYEE table if already exists.
cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")
sql = '''CREATE TABLE EMPLOYEE(
FIRST_NAME CHAR(20) NOT NULL,
LAST_NAME CHAR(20),
AGE INT,
SEX CHAR(1),
INCOME FLOAT
)'''
cursor.execute(sql)
#Populating the table
insert_stmt = "INSERT INTO EMPLOYEE (FIRST_NAME, LAST_NAME, AGE, SEX, INCOME)
VALUES (%s, %s, %s, %s, %s)"
data = [('Krishna', 'Sharma', 26, 'M', 2000),
('Raj', 'Kandukuri', 20, 'M', 7000),
('Ramya', 'Ramapriya', 29, 'F', 5000),
('Mac', 'Mohan', 26, 'M', 2000)]
cursor.executemany(insert_stmt, data)
conn.commit()
#Retrieving specific records using the ORDER BY clause
cursor.execute("SELECT * from EMPLOYEE ORDER BY AGE")
print(cursor.fetchall())
#Closing the connection
conn.close()Output
[('Raj', 'Kandukuri', 20, 'M', 7000.0),
('Krishna', 'Sharma', 26, 'M', 2000.0),
('Mac', 'Mohan', 26, 'M', 2000.0),
('Ramya', 'Ramapriya', 29, 'F', 5000.0)
]同样，你可以使用 ORDER BY 子句按降序从表中检索数据。
Example
import mysql.connector
#establishing the connection
conn = mysql.connector.connect(
user='root', password='password', host='127.0.0.1', database='mydb')
#Creating a cursor object using the cursor() method
cursor = conn.cursor()
#Retrieving specific records using the ORDERBY clause
cursor.execute("SELECT * from EMPLOYEE ORDER BY INCOME DESC")
print(cursor.fetchall())
#Closing the connection
conn.close()