Python MySQL Order By
当使用SELECT查询获取数据时,你可以使用OrderBy子句将结果按所需顺序(升序或降序)排序。默认情况下,该子句以升序排列结果,如果你需要以降序排列,你需要明确使用 “DESC”。
语法
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:
例子
Assume we have created a table in MySQL with name EMPLOYEES as −
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)
如果我们使用INSERT语句在其中插入4条记录,如:
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);
下面的语句按照年龄的升序检索EMPLAYEE表中的内容。
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)
You can also retrieve data in descending order using DESC as −
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)
使用python的ORDER BY子句
为了按照特定的顺序检索表的内容,在游标对象上调用 execute() 方法,并将SELECT语句和ORDER BY子句作为参数传递给它。
例子
在下面的例子中,我们创建了一个包含姓名和雇员的表,填充它,并使用ORDER BY子句按照年龄的(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()
输出
[('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子句从表中以降序检索数据。
例子
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()
输出
[('Raj', 'Kandukuri', 20, 'M', 7000.0),
('Ramya', 'Ramapriya', 29, 'F', 5000.0),
('Krishna', 'Sharma', 26, 'M', 2000.0),
('Mac', 'Mohan', 26, 'M', 2000.0)
]