python----积累---使用传参的方式构造sql语句

Posted 2021-11-23 张小凡vip

使用pymsql查询数据如下：

import pymysql

conn=pymysql.connect(host='123',
                           port=3306,
                           user=root',
                           password='12345',
                           database='school',
                           charset='utf8')



results = []


sql = """
select * from students where class in ('3班','4班','6班','8班')  and province in  ('北京','广西','四川','云南')
"""

# print(sql)

try:
    cursor = pymysql.cursors.SSCursor(conn)
    result=cursor.execute(sql)
    while True:
        row = cursor.fetchone()
#         print(row)
        if not row:
            print("finish")
            break
        results.append((row[0],row[1],row[2],str(row[1])+str(row[2])))
except:
   print("Error: unable to fecth data")

这样的用法sql语句适合 少量的参数变量，但是 当变量值 成千上万个时，就需要 把参数提取出来，通过传参的方式进行构造。

方案一

import pymysql

conn=pymysql.connect(host='123',
                           port=3306,
                           user=root',
                           password='12345',
                           database='school',
                           charset='utf8')



class_list=['3班','4班','6班','8班']

province_list=['北京','广西','四川','云南']

results = []


sql = """
select * from students where class in {} and province in {}
""".format(tuple(class_list),tuple(province_list))

# print(sql)

try:
    cursor = pymysql.cursors.SSCursor(conn)
    result=cursor.execute(sql)
    while True:
        row = cursor.fetchone()
#         print(row)
        if not row:
            print("finish")
            break
        results.append((row[0],row[1],row[2],str(row[1])+str(row[2])))
except:
   print("Error: unable to fecth data")

方案二

select_str = 'select * from server where ip in (%s)' % ','.join(['%s'] * len(a))     
>>> select_str
'select * from server where ip in (%s,%s,%s)'
这里我们先根据Ip列表的长度来生成对应的参数位置，然后通过MySQLdb模块中的execute函数来执行：
cursor.execute(select_str,a)




import pymysql

conn=pymysql.connect(host='123',
                           port=3306,
                           user=root',
                           password='12345',
                           database='school',
                           charset='utf8')



class_list=['3班','4班','6班','8班']

province_list=['北京','广西','四川','云南']

results = []


sql = 'select * from students where class in   (%s) and province in   (%s) ' % ( ','.join(['%s'] * len(class_list)),  ','.join(['%s'] * len(province_list)) )

# print(sql)





try:
    cursor = pymysql.cursors.SSCursor(conn)
    result=cursor.execute(sql,class_list,province_list)
    while True:province_list
        row = cursor.fetchone()
#         print(row)
        if not row:
            print("finish")
            break
        results.append((row[0],row[1],row[2],str(row[1])+str(row[2])))
except:
   print("Error: unable to fecth data")