python與MySQL數據庫的交互——筆記
python3中庫pymysql的使用
基本用法(連接SQL,執行SQL語句)
# 導入pymysql模塊
import pymysql
# 連接database
conn = pymysql.connect(host=“你的數據庫地址”, user=“用戶名”,password=“密碼”,database=“數據庫名”,charset=“utf8”)
# 得到一個可以執行SQL語句的光標對象
cursor = conn.cursor()
# 定義要執行的SQL語句
sql = """
CREATE TABLE USER1 (
id INT auto_increment PRIMARY KEY ,
name CHAR(10) NOT NULL UNIQUE,
age TINYINT NOT NULL
)ENGINE=innodb DEFAULT CHARSET=utf8;
"""
# 執行SQL語句
cursor.execute(sql)
# 關閉光標對象
cursor.close()
# 關閉數據庫連接
conn.close()
包裝成類代碼
class Mysql(object):
def __init__(self):
try:
self.conn = pymysql.connect(
host='127.0.0.1',
port=3306,
user='root',
passwd='123456',
db='test',
charset='utf8'
)
except Exception as e:
print(e)
else:
print('連接成功')
self.cur = self.conn.cursor()
def create_table(self):
sql = 'create table testtb(id int, name varchar(10),age int)'
res = self.cur.execute(sql)
print(res)
def close(self):
self.cur.close()
self.conn.close()
def add(self): # 增
sql = 'insert into testtb values(1,"Tom",18),(2,"Jerry",16),(3,"Hank",24)'
res = self.cur.execute(sql)
if res:
self.conn.commit()
else:
self.conn.rollback()
print(res)
def rem(self): # 刪
sql = 'delete from testtb where id=1'
res = self.cur.execute(sql)
if res:
self.conn.commit()
else:
self.conn.rollback()
print(res)
def mod(self): # 改
sql = 'update testtb set name="Tom Ding" where id=2'
res = self.cur.execute(sql)
if res:
self.conn.commit()
else:
self.conn.rollback()
print(res)
def show(self): # 查
sql = 'select * from testtb'
self.cur.execute(sql)
res = self.cur.fetchall()
for i in res:
print(i)
if __name__ == "__main__":
mysql = Mysql()
mysql.create_table()
mysql.add()
mysql.mod()
mysql.rem()
mysql.show()
mysql.close()
其中的函數註解:
# ret = self.cur.execute(sql) # 返回內容的條數
# print(ret)
res = self.cur.fetchall() # 返回元祖類型<class 'tuple'>
# print(type(res))
for i in res:
print(i)
# 得到一個可以執行SQL語句並且將結果作爲字典返回的遊標
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
結果如圖(字典顯示):
原先的結果顯示(元祖類型):
“增刪改查”操作
“增”
注意字符串的拼接技巧
sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);"
username = "Alex"
age = 18
# 執行SQL語句
cursor.execute(sql, [username, age])
有異常回滾事務
try:
# 執行SQL語句
cursor.execute(sql, [username, age])
# 提交事務
conn.commit()
except Exception as e:
print(e)
# 有異常,回滾事務
conn.rollback()
批量插入數據
# 導入pymysql模塊
import pymysql
# 連接database
conn = pymysql.connect(host=“你的數據庫地址”, user=“用戶名”,password=“密碼”,database=“數據庫名”,charset=“utf8”)
# 得到一個可以執行SQL語句的光標對象
cursor = conn.cursor()
sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);"
data = [("Alex", 18), ("Egon", 20), ("Yuan", 21)]
try:
# 批量執行多條插入SQL語句
cursor.executemany(sql, data)
# 提交事務
conn.commit()
except Exception as e:
# 有異常,回滾事務
conn.rollback()
cursor.close()
conn.close()
“刪”
sql = "DELETE FROM USER1 WHERE id=%s;"
try:
cursor.execute(sql, [4])
# 提交事務
conn.commit()
except Exception as e:
# 有異常,回滾事務
conn.rollback()
“改”
# 修改數據的SQL語句
sql = "UPDATE USER1 SET age=%s WHERE name=%s;"
username = "Alex"
age = 80
try:
# 執行SQL語句
cursor.execute(sql, [age, username])
# 提交事務
conn.commit()
except Exception as e:
# 有異常,回滾事務
conn.rollback()
“查”
查詢多條數據:
# 編寫sql 查詢語句 user 對應我的表名
sql = "select * from user"
try:
cur.execute(sql) #執行sql語句
results = cur.fetchall() #獲取查詢的所有記錄
print("id","name","password")
#遍歷結果
for row in results :
id = row[0]
name = row[1]
password = row[2]
print(id,name,password)
except Exception as e:
raise e
finally:
db.close() #關閉連接
查詢單條數據:
# 查詢數據的SQL語句
sql = "SELECT id,name,age from USER1 WHERE id=1;"
# 執行SQL語句
cursor.execute(sql)
# 獲取單條查詢數據,取第一條
ret = cursor.fetchone()
指定數量:
cursor.fetchmany(3)