psycopg2:使用元组元组中的值更新表中的多行 [英] psycopg2: Update multiple rows in a table with values from a tuple of tuples

问题描述

我正在尝试使用元组元组一次更新多行.我想出了如何从 这篇文章 构建 sql 语句，但事实证明，在 psycopg2 中实现它更具挑战性.这是我所拥有的:

I'm attempting to update several rows at once using a tuple of tuples. I figured out how to construct the sql statement from this post, but implementing it in psycopg2 has proven to be more challenging. Here's what I have:

c = db.cursor()

new_values = (("Richard",29),("Ronald",30))

sql = """UPDATE my_table AS t 
         SET name = e.name 
         FROM (VALUES %s) AS e(name, id) 
         WHERE e.id = t.id;"""

c.execute(sql, (new_values,))

结果是一个错误:ProgrammingError: table "e" has 1 columns available but 2 columns specified这是因为 FROM 子句被解释为:

The result is an error: ProgrammingError: table "e" has 1 columns available but 2 columns specified This is because the FROM clause is being interpreted as:

FROM (VALUES (("Richard",29),("Ronald",30)))

代替:

FROM (VALUES ("Richard",29),("Ronald",30))

我可以通过执行以下操作来解决此问题，但它似乎不安全:

I can work around this by doing the following but it seems unsafe:

import re
c = db.cursor()

sql = """UPDATE my_table AS t 
         SET name = e.name 
         FROM (VALUES %s) AS e(name, id) 
         WHERE e.id = t.id;"""
sql = c.mogrify(sql, (new_values,))

# Replace the first occurance of '((' with '('.
sql = sql.replace('((', '(',1)

# Replace the last occurance of '))' with ')'.
sql = re.sub(r'(.*)\)\)', r'\1)', sql)

sql = c.execute(sql)

有没有更好的方法来做到这一点?

Is there a better way to do this?

推荐答案

这篇文章 为我指明了正确的方向.文档 extras.execute_values还包含一个使用 UPDATE 子句的好例子.

This post pointed me in the right direction. The documentation for extras.execute_values also contains a great example using the UPDATE clause.

c = db.cursor()
update_query = """UPDATE my_table AS t 
                  SET name = e.name 
                  FROM (VALUES %s) AS e(name, id) 
                  WHERE e.id = t.id;"""

psycopg2.extras.execute_values (
    c, update_query, new_values, template=None, page_size=100
)

这篇关于psycopg2:使用元组元组中的值更新表中的多行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！