sqlite3 学习笔记

12月5日集中学习了一下python标准库中的sqlite3，看了廖雪峰、vamei，《python语言及其运用》三个教程，笔记如下

#廖雪峰教程  http://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/001388320596292f925f46d56ef4c80a1c9d8e47e2d5711000
import sqlite3   # 导入SQLite驱动:
# 连接到SQLite数据库, 数据库文件是test.db
# 如果文件不存在，会自动在当前目录创建:
conn = sqlite3.connect('test.db')
# 创建一个Cursor:
cursor = conn.cursor()
# 执行一条SQL语句，创建user表:
cursor.execute('create table user (id varchar(20) primary key, name varchar(20))')
# 继续执行一条SQL语句，插入一条记录:
cursor.execute('insert into user (id, name) values (\'1\', \'Michael\')')
cursor.rowcount   #通过rowcount获得插入的行数:
cursor.close()    #关闭Cursor:
conn.commit()     #提交事务:
conn.close()      #关闭Connection


# By Vamei  创建数据库 http://www.cnblogs.com/vamei/p/3794388.html
import sqlite3
# test.db is a file in the working directory.
conn = sqlite3.connect("test.db")
cursor = conn.cursor()
# create tables
cursor.execute('''CREATE TABLE category
      (id int primary key, sort int, name text)''')
cursor.execute('''CREATE TABLE book
      (id int primary key, 
       sort int, 
       name text, 
       price real, 
       category int,
       FOREIGN KEY (category) REFERENCES category(id))''')
conn.commit()   # save the changes
conn.close()     # close the connection with the database


#Vamei 插入数据
import sqlite3
conn = sqlite3.connect("test.db")
c    = conn.cursor()
books = [(1, 1, 'Cook Recipe', 3.12, 1),
            (2, 3, 'Python Intro', 17.5, 2),
            (3, 2, 'OS Intro', 13.6, 2)]
 # execute "INSERT" 
c.execute("INSERT INTO category VALUES (1, 1, 'kitchen')")

# using the placeholder
c.execute("INSERT INTO category VALUES (?, ?, ?)", [(2, 2, 'computer')])

# execute multiple commands
c.executemany('INSERT INTO book VALUES (?, ?, ?, ?, ?)', books)
conn.commit()
conn.close()


# By Vamei   查询数据
import sqlite3
conn = sqlite3.connect('test.db')
c = conn.cursor()
# retrieve one record
c.execute('SELECT name FROM category ORDER BY sort')
print(c.fetchone())
print(c.fetchone())
# retrieve all records as a list
c.execute('SELECT * FROM book WHERE book.category=1')
print(c.fetchall())
# iterate through the records
for row in c.execute('SELECT name, price FROM book ORDER BY sort'):
    print(row)
    

# By Vamei  更新与删除
conn = sqlite3.connect("test.db")
c = conn.cursor()
c.execute('UPDATE book SET price=? WHERE id=?',(1000, 1))
c.execute('DELETE FROM book WHERE id=2')
conn.commit()
conn.close()
c.execute('DROP TABLE book')  #删除整张表