python之数据库编程

python之数据库编程

sqlite

1.前期准备工作

• 导入模块：

  import sqlite3
  

• 连接数据库

  conn = sqlite3.connect("test.db")  #test为数据库名称，若不存在此数据库，会自动创建
  

• 测试是否创建或连接数据库成功

  print(conn)  #打印结果为connection对象
  

• pycharm端显示出数据库：

  • 1.打开pycharm->右端database->点击+号
    
    

• 2.第二步：

  

• 3.第三步
  
  

• 4.选择pycharm工作环境下新创建的数据库，比如我的在这里
  
  

点击ok即可，注意：

若第三步出现这个，点击Download先进行下载。。。

2.创建数据库和表

import sqlite3
conn = sqlite3.connect("test.db")
#cur = conn.cursor()
sql = """
CREATE TABLE test(
id INTEGER PRIMARY KEY autoincrement,
name TEXT,
age INTEGER
)
"""
try:
    #cur.execute(sql)
    conn.execute(sql)
except Exception as e:
    print(e)
finally:
    #cur.close()
    conn.close()

注意：

​ 可以看到，此处并没有使用游标，而是直接conn.execute(sql)，值得说明的是，对sqlite来说（mysql却不是），增删改以及创建表都可以不用游标，但查询一定需要，往下看

3.插入数据

import sqlite3
conn = sqlite3.connect('test.db')
# cur = conn.cursor()
sql = """
insert into test(name, age) VALUES (%s,%s)
"""%("'王五'",22)
sql1 = """
insert into test(name, age) VALUES (?,?)
"""
try:
    print("sql:"+sql)
    print("sql1:" + sql1)
    #conn.execute(sql)
    #conn.execute(sql1, ('张三', 20))添加单条数据
    conn.executemany(sql1,[('李四',18),('王五',28),('赵六',38)])
    conn.commit()
    print("插入成功")
except Exception as e:
    print(e)
    print("插入失败")
    conn.rollback()
finally:
    conn.close()

显示结果：

插入数据中使用了两种方法，见sql和sql1，分别使用%s和?占位符

以下我就不一一展示显示结果了。。。

4.修改数据

import sqlite3
conn = sqlite3.connect('test.db')
# cur = conn.cursor()
sql = """
update test set name = ? , age = ? where id = ?
"""
sql1 = """
update test set name = %s , age = %s where id = %s
"""%("'曹操'", 24, 11)
try:
    #conn.execute(sql, ('曹操', 24, 4))
    conn.execute(sql1)
    print("成功")
    conn.commit()
except Exception as e:
    print(e)
    print("失败")
    conn.rollback()
finally:
    conn.close()

修改数据中使用了两种方法，见sql和sql1，分别使用%s和?占位符

5.删除数据

import sqlite3
conn = sqlite3.connect('test.db')
#cur = conn.cursor()
sql = """
delete from test where name = ?
"""
sql1 = """
delete from test where name = %s
"""%("'曹操'",)
try:
    conn.execute(sql1);
    #conn.execute(sql,('曹操',));
    #若执行conn.execute(sql,('曹操'));会报错Incorrect number of bindings supplied. The current statement uses 1, and there are 2 supplied.
    #使用('曹操',)或[曹操]
    conn.commit()
except Exception as e:
    conn.rollback()
    print(e)
finally:
    conn.close()

6.查询数据

import sqlite3
conn = sqlite3.connect('test.db')
cur = conn.cursor()
sql = """
select * from test
"""
try:
    cur.execute(sql);
    # print(cur.fetchall())#查询所有数据
    print(cur.fetchone())  # 查询第一条数据
    # print(cur.fetchmany(3))#查询几条数据，从开头开始
except Exception as e:
    print(e)
finally:
    cur.close()
    conn.close()

可以看到，查询数据必须要用游标，按条件进行查询可参照上面的占位符进行测试

7.模糊查询

import sqlite3
conn = sqlite3.connect('test.db')
cur = conn.cursor()
sql = "select * from test where name like '%%%s%%'"%"王"
#sql1 = "select * from test where name like ?"
try:
    print(sql)
    cur.execute(sql);
    #cur.execute(sql1, ("%王%",));
    print(cur.fetchall())  # 查询所有数据
    # print(cur.fetchone())  # 查询第一条数据
    # print(cur.fetchmany(3))#查询几条数据，从开头开始
except Exception as e:
    print(e)
finally:
    cur.close()
    conn.close()

模糊查询中使用了两种方法，见sql和sql1，分别使用%s和?占位符

注意：%s占位符模糊查询时，使用%%---%%进行转义

mysql

1.前期准备工作

• 导入模块：

  import pymysql
  

• 连接数据库

  conn = pymysql.connect(user='root',password='000000',host='localhost',
                         port=3306,database='python_test')
  #mysql数据库不会自动创建，需要自己建立
  

• 测试是否连接数据库成功

  print(conn)  #打印结果为connection对象
  

• pycharm端显示出数据库：

​ 与sqlite操作一样，此时建立的是mysql

2.创建数据库和表

import pymysql
conn = pymysql.connect(user='root',password='000000',host='localhost',
                       port=3306,database='python_test')
cur = conn.cursor()
sql = """
create table student(
id integer primary key auto_increment,
sno char(20) not null,
name char(20),
score float
)
"""
try:
    cur.execute(sql)
    print("建表成功")
except Exception as e:
    print(e)
    print("建表失败")
finally:
    cur.close()
    conn.close()

注意：

​ 可以看到，与sqlite不同，mysql的操作都需要游标参与

3.插入数据

import pymysql
conn = pymysql.connect(user='root', password='000000', host='localhost', port=3306, database='python_test')
cur = conn.cursor()
sql = """
insert into student(sno, name, score)
values
(%s,%s,%s)
"""
try:
    #cur.execute(sql, ('7777', 'ff', 90))  #插入一条
    cur.executemany(sql,[('3333','c',3),('4444','d',4)])  #插入多条
    conn.commit()
    print("插入成功")
except Exception as e:
    print(e)
    conn.rollback()
    print("插入失败")
finally:
    cur.close()
    conn.close()

显示结果：

mysql中使用%s做占位符

4.修改数据

import pymysql
conn = pymysql.connect(user='root', password='000000', host='localhost', port=3306, database='python_test')
cur = conn.cursor()
sql = """
update student set name = %s where id = %s
"""
try:
    cur.execute(sql,('王五',5))
    #cur.executemany(sql,[('3333','c',3),('4444','d',4)])
    conn.commit()
    print("修改成功")
except Exception as e:
    print(e)
    conn.rollback()
    print("修改失败")
finally:
    cur.close()
    conn.close()

5.删除数据

import pymysql

conn = pymysql.connect(user='root', password='000000', host='localhost', port=3306, database='python_test')
cur = conn.cursor()
sql = """
 delete from student where name = %s
"""
try:
    cur.execute(sql,'d')
    #cur.executemany(sql,[('3333','c',3),('4444','d',4)])
    conn.commit()
    print("删除成功")
except Exception as e:
    print(e)
    conn.rollback()
    print("删除失败")
finally:
    cur.close()
    conn.close()

6.查询数据

import pymysql

conn = pymysql.connect(user='root', password='000000', host='localhost', port=3306, database='python_test')
cur = conn.cursor()
sql = """
select * from student
"""
try:
    cur.execute(sql)
    #print(cur.fetchone())
    #print(cur.fetchmany(3))
    print(cur.fetchall())
except Exception as e:
    print(e)
finally:
    cur.close()
    conn.close()

7.模糊查询

import pymysql

conn = pymysql.connect(user='root', password='000000', host='localhost', port=3306, database='python_test')
cur = conn.cursor()
sql = """
select * from student where name like %s
"""
sql1 = "select * from student where name like '%%%s%%'"%'王'
try:
    print(sql1)
    cur.execute(sql1)
    #print(cur.fetchone())
    #print(cur.fetchmany(3))
    print(cur.fetchall())
except Exception as e:
    print(e)
finally:
    cur.close()
    conn.close()