即使在我执行 commit() 和 autocommit=True 后也无法使用 psycopg2 脚本更新 PostgreSQL 表

Question

我正在尝试使用 psycopg2 游标更新在 ElephantSQL 服务上运行的 PostgreSQL 表。从我的计算机 (MacOS) 执行 SQL 语句。该脚本认为一切正常，但表未更新。我已经指定了“connection.autocommit=True”并且还在 cursor.execute(SQL) 语句之后包含了“connection.commit()”语句。什么都不管用。帮助将不胜感激。

这是一个代码片段：

# Establish Connection
try:
    connection = psycopg2.connect(conn_string)
    connection.autocommit=True
except Exception as e:
    print("******Cannot connect to DB****** \n" + "error: " + str(e))
    exit()



# ---   Later on,  when trying to update the DB

if request.method == "POST":
        if form.validate_on_submit():
            username_to_delete = request.form['username']
            print(" username to delete is: " + username_to_delete)
            try:
                with connection, connection.cursor() as cursor:
                        cursor.execute("DELETE FROM users WHERE username='username_to_delete';")
                        connection.commit()
                        cursor.close()
            except Exception as e:
                flash("Delete operation failed, error: " + str(e)) 
                print("Delete operation failed, try again ..." + str(e))
                return render_template("delete_user.html", form=form)
            flash("User Deleted Successfully!!")
            username_to_delete = ""
            return render_template("delete_user.html", form=form)
    
        else:
            print(" Error with Delete Form validation")
            flash(" There was a problem deleting user, try again...")
        return render_template("delete_user.html", form=form)

    else:
        flash(" User Delete failed! -  form problems")  
        return render_template("delete_user.html", form=form)

正如我提到的，脚本报告用户已成功删除，但事实并非如此。

正如我所说，我整天都在为此挠头。希望有人能指出我正确的方向。

我尝试将自动提交属性添加到连接中，并且还在事务之后添加了 connection.commit() 语句。不知何故，这对我不起作用。非常感谢您的帮助。

Answer 1

问题的答案与 DB commit() 或 autocommit=True 无关。

正如评论所指出的，我错误地传递了所需的参数。

cursor.execute 语句不正确，因为没有将元组作为语句的第二部分传递。

    try:
                with connection, connection.cursor() as cursor:
                        cursor.execute("DELETE FROM users WHERE id=%s;",(id_to_delete,))
                        connection.commit()
                        cursor.close()
            except Exception as e:
                flash("Delete operation failed, error: " + str(e)) 
                print("Delete operation failed, try again ..." + str(e))
                return render_template("delete_user.html", form=form)

所以语句应该是：cursor.execute("SELECT id FROM users WHERE username=%s;", (username,)) 。最后一部分：（用户名，）之前没有正确完成。感谢 Richard Hutton 和 Adrian Klaver。您的意见帮助我解决了这个问题。