Python "INSERT INTO"与 "INSERT INTO...ON DUPLICATE KEY UPDATE"

Question

我正在尝试使用 python 将记录插入 MySQL 数据库，然后更新该记录。为此，我创建了 2 个函数:

def insert_into_database():

query = "INSERT INTO pcf_dev_D.users(user_guid,username) VALUES (%s, %s) "
data = [('1234', 'user1234')]
parser = ConfigParser()
parser.read('db/db_config.ini')
db = {}
section = 'mysql'

if parser.has_section(section):
    items = parser.items(section)
    for item in items:
        db[item[0]] = item[1]
else:
    raise Exception('{0} not found in the {1} file'.format(section, filename))

try:
    conn = MySQLConnection(**db)
    cursor = conn.cursor()
    cursor.executemany(query, data)
    conn.commit()
except Error as e:
    print('Error:', e)
finally:
    # print("done...")
    cursor.close()
    conn.close()

这工作正常并将 1234、user1234 插入到数据库中。

现在我想将这个特定用户的用户名更新为“5678”，所以我创建了另一个函数:

def upsert_into_database():

query = "INSERT INTO pcf_dev_D.users(user_guid,username) " \
        "VALUES (%s, %s) ON DUPLICATE KEY UPDATE username='%s'"
data = [('1234', 'user1234', 'user5678')]
parser = ConfigParser()
parser.read('db/db_config.ini')
db = {}
section = 'mysql'

if parser.has_section(section):
    items = parser.items(section)
    for item in items:
        db[item[0]] = item[1]
else:
    raise Exception('{0} not found in the {1} file'.format(section, 'db/db_config.ini'))

try:
    conn = MySQLConnection(**db)
    cursor = conn.cursor()
    cursor.executemany(query, data)
    conn.commit()
except Error as e:
    print('Error:', e)
finally:
    # print("done...")
    cursor.close()
    conn.close()

这会产生以下错误: 错误:SQL 语句中未使用所有参数

有趣的是，如果我将查询和数据修改为:

query = "INSERT INTO pcf_dev_D.users(user_guid,username) " \
        "VALUES (%s, %s) ON DUPLICATE KEY UPDATE username='user5678'"
data = [('1234', 'user1234')]

然后 python 更新记录就好了......我错过了什么？

Answer 1

您在 update 子句中将第三个参数包含在单引号内，因此它被解释为字符串的一部分，而不是参数的占位符。您不能用引号将参数括起来:

query = "INSERT INTO pcf_dev_D.users(user_guid,username) " \
        "VALUES (%s, %s) ON DUPLICATE KEY UPDATE username=%s"

更新

如果您想将 on duplicate key update 子句与批量插入一起使用(例如 executemany())，那么您不应在 中提供任何参数>update 子句，因为在批量插入语句中只能有一个更新子句。使用 values()代替函数:

query = "INSERT INTO pcf_dev_D.users(user_guid,username) " \
        "VALUES (%s, %s) ON DUPLICATE KEY UPDATE username=VALUES(username)"

In assignment value expressions in the ON DUPLICATE KEY UPDATE clause, you can use the VALUES(col_name) function to refer to column values from the INSERT portion of the INSERT ... ON DUPLICATE KEY UPDATE statement. In other words, VALUES(col_name) in the ON DUPLICATE KEY UPDATE clause refers to the value of col_name that would be inserted, had no duplicate-key conflict occurred. This function is especially useful in multiple-row inserts. The VALUES() function is meaningful only in the ON DUPLICATE KEY UPDATE clause or INSERT statements and returns NULL otherwise.