Python SQLite - Order By 子句

使用 SELECT 查询获取数据时，您将按照插入记录的相同顺序获取记录。

您可以使用 Order By 子句按所需顺序（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，如果您需要按降序排列它们，则需要明确使用"DESC"。

语法

以下是 SQLite 中 ORDER BY 子句的语法。

SELECT column-list
FROM table_name
[WHERE condition]
[ORDER BY column1, column2, .. columnN] [ASC | DESC];

示例

假设我们使用以下查询创建了一个名为 Basketball 的表 −

sqlite> CREATE TABLE Basketball (
   First_Name VARCHAR(255),
   Last_Name VARCHAR(255),
   Age int,
   Place_Of_Birth VARCHAR(255),
   Country VARCHAR(255)
);
sqlite>

如果我们使用 INSERT 语句将 5 条记录插入其中 −

sqlite> insert into Basketball values('Shikhar', 'Dhawan', 33, 'Delhi', 'India');
sqlite> insert into Basketball values('Jonathan', 'Trott', 38, 'CapeTown', 'SouthAfrica');
sqlite> insert into Basketball values('Kumara', 'Sangakkara', 41, 'Matale', 'Srilanka');
sqlite> insert into Basketball values('Virat', 'Kohli', 30, 'Delhi', 'India');
sqlite> insert into Basketball values('Rohit', 'Sharma', 32, 'Nagpur', 'India');
sqlite>

以下 SELECT 语句按年龄的升序检索 Basketball 表中的行 −

sqlite> SELECT * FROM Basketball ORDER BY AGE;
First_Name   Last_Name    Age    Place_Of_B   Country
----------   ----------   ----   ----------   -----------
Virat        Kohli        30     Delhi        India
Rohit        Sharma       32     Nagpur       India
Shikhar      Dhawan       33     Delhi        India
Jonathan     Trott        38     CapeTown     SouthAfrica
Kumara       Sangakkara   41     Matale       Srilanka
sqlite>

您可以使用多个列来对表格的记录进行排序。 以下 SELECT 语句根据 AGE 和 FIRST_NAME 列对 Basketball 表的记录进行排序。

sqlite> SELECT * FROM Basketball ORDER BY AGE, FIRST_NAME;
First_Name   Last_Name    Age    Place_Of_B   Country
----------   ----------   ----   ----------   -------------
Virat        Kohli        30     Delhi        India
Rohit        Sharma       32     Nagpur       India
Shikhar      Dhawan       33     Delhi        India
Jonathan     Trott        38     CapeTown     SouthAfrica
Kumara       Sangakkara   41     Matale       Srilanka
sqlite>

默认情况下，ORDER BY 子句按升序对表的记录进行排序，您可以使用 DESC 将结果按降序排列，如下所示 −

sqlite> SELECT * FROM Basketball ORDER BY AGE DESC;
First_Name   Last_Name    Age    Place_Of_B   Country
----------   ----------   ----   ----------   -------------
Kumara       Sangakkara   41     Matale       Srilanka
Jonathan     Trott        38     CapeTown     SouthAfrica
Shikhar      Dhawan       33     Delhi        India
Rohit        Sharma       32     Nagpur       India
Virat        Kohli        30     Delhi        India
sqlite>

使用 Python 的 ORDER BY 子句

要按特定顺序检索表的内容，请对游标对象调用 execute() 方法，并将 SELECT 语句连同 ORDER BY 子句作为参数传递给它。

示例

在下面的示例中，我们将使用 ORDER BY 子句创建一个包含名称和员工的表，填充它，并按年龄的（升序）顺序检索其记录。

import psycopg2
#establishing the connection
conn = psycopg2.connect(
   database="mydb", user='postgres', password='password', host='127.0.0.1', port= '5432'
)

#Setting auto commit false
conn.autocommit = True

#Creating a cursor object using the cursor() method
cursor = conn.cursor()

#Doping EMPLOYEE table if already exists.
cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")
#Creating a table
sql = '''CREATE TABLE EMPLOYEE(
   FIRST_NAME CHAR(20) NOT NULL,
   LAST_NAME CHAR(20),
   AGE INT, SEX CHAR(1),
   INCOME INT,
   CONTACT INT
)'''
cursor.execute(sql)
#Populating the table
#Populating the table
cursor.execute(
   '''INSERT INTO EMPLOYEE(FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) 
   VALUES ('Ramya', 'Rama priya', 27, 'F', 9000),
   ('Vinay', 'Battacharya', 20, 'M', 6000), 
   ('Sharukh', 'Sheik', 25, 'M', 8300), 
   ('Sarmista', 'Sharma', 26, 'F', 10000),
   ('Tripthi', 'Mishra', 24, 'F', 6000)''')
conn.commit()

#Retrieving specific records using the ORDER BY clause
cursor.execute("SELECT * from EMPLOYEE ORDER BY AGE")

print(cursor.fetchall())

#Commit your changes in the database
conn.commit()

#Closing the connection
conn.close()

输出

[
   ('Vinay', 'Battacharya', 20, 'M', 6000, None),
   ('Tripthi', 'Mishra', 24, 'F', 6000, None),
   ('Sharukh', 'Sheik', 25, 'M', 8300, None),
   ('Sarmista', 'Sharma', 26, 'F', 10000, None),
   ('Ramya', 'Rama priya', 27, 'F', 9000, None)
]