SQLite – Python

SQLite - Python

安裝

SQLite3 可使用 sqlite3 模組與 Python 進行整合。sqlite3 模組是由 Gerhard Haring 編寫的。它提供了一個與 PEP 249 描述的 DB-API 2.0 規範相容的 SQL 介面。您不需要單獨安裝該模組，因為 Python 2.5.x 以上版本預設自帶了該模組。

為了使用 sqlite3 模組，您首先必須建立一個表示資料庫的連線物件，然後您可以有選擇地建立游標物件，這將幫助您執行所有的 SQL 語句。

Python sqlite3 模組 API

以下是重要的 sqlite3 模組程式，可以滿足您在 Python 程式中使用 SQLite 資料庫的需求。如果您需要了解更多細節，請檢視 Python sqlite3 模組的官方文件。

連線資料庫

下面的 Python 程式碼顯示瞭如何連線到一個現有的資料庫。如果資料庫不存在，那麼它就會被建立，最後將返回一個數據庫物件。

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('test.db')

print "Opened database successfully"

在這裡，您也可以把資料庫名稱複製為特定的名稱 :memory:，這樣就會在 RAM 中建立一個數據庫。現在，讓我們來執行上面的程式，在當前目錄中建立我們的資料庫 test.db。您可以根據需要改變路徑。儲存上面程式碼到 sqlite.py 檔案中，並按如下所示執行。如果資料庫成功建立，那麼會顯示下面所示的訊息：

$chmod +x sqlite.py
$./sqlite.py
Open database successfully

建立表

下面的 Python 程式碼段將用於在先前建立的資料庫中建立一個表：

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('test.db')
print "Opened database successfully"
c = conn.cursor()
c.execute('''CREATE TABLE COMPANY
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print "Table created successfully"
conn.commit()
conn.close()

上述程式執行時，它會在 test.db 中建立 COMPANY 表，並顯示下面所示的訊息：

Opened database successfully
Table created successfully

INSERT 操作

下面的 Python 程式顯示瞭如何在上面建立的 COMPANY 表中建立記錄：

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully"

c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (1, 'Paul', 32, 'California', 20000.00 )")

c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (2, 'Allen', 25, 'Texas', 15000.00 )")

c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (3, 'Teddy', 23, 'Norway', 20000.00 )")

c.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 )")

conn.commit()
print "Records created successfully"
conn.close()

上述程式執行時，它會在 COMPANY 表中建立給定記錄，並會顯示以下兩行：

Opened database successfully
Records created successfully

SELECT 操作

下面的 Python 程式顯示瞭如何從前面建立的 COMPANY 表中獲取並顯示記錄：

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully"

cursor = c.execute("SELECT id, name, address, salary  from COMPANY")
for row in cursor:
   print "ID = ", row[0]
   print "NAME = ", row[1]
   print "ADDRESS = ", row[2]
   print "SALARY = ", row[3], "\n"

print "Operation done successfully"
conn.close()

上述程式執行時，它會產生以下結果：

Opened database successfully
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  20000.0

ID =  2
NAME =  Allen
ADDRESS =  Texas
SALARY =  15000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

UPDATE 操作

下面的 Python 程式碼顯示瞭如何使用 UPDATE 語句來更新任何記錄，然後從 COMPANY 表中獲取並顯示更新的記錄：

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully"

c.execute("UPDATE COMPANY set SALARY = 25000.00 where ID=1")
conn.commit()
print "Total number of rows updated :", conn.total_changes

cursor = conn.execute("SELECT id, name, address, salary  from COMPANY")
for row in cursor:
   print "ID = ", row[0]
   print "NAME = ", row[1]
   print "ADDRESS = ", row[2]
   print "SALARY = ", row[3], "\n"

print "Operation done successfully"
conn.close()

上述程式執行時，它會產生以下結果：

Opened database successfully
Total number of rows updated : 1
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  25000.0

ID =  2
NAME =  Allen
ADDRESS =  Texas
SALARY =  15000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

DELETE 操作

下面的 Python 程式碼顯示瞭如何使用 DELETE 語句刪除任何記錄，然後從 COMPANY 表中獲取並顯示剩餘的記錄：

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('test.db')
c = conn.cursor()
print "Opened database successfully"

c.execute("DELETE from COMPANY where ID=2;")
conn.commit()
print "Total number of rows deleted :", conn.total_changes

cursor = conn.execute("SELECT id, name, address, salary  from COMPANY")
for row in cursor:
   print "ID = ", row[0]
   print "NAME = ", row[1]
   print "ADDRESS = ", row[2]
   print "SALARY = ", row[3], "\n"

print "Operation done successfully"
conn.close()

上述程式執行時，它會產生以下結果：

Opened database successfully
Total number of rows deleted : 1
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  20000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully