将数据库导入 MATLAB 错误 [英] Importing a Database to MATLAB error

问题描述

我正在尝试将表导入到我的 MATLAB 工作区，但它不断向我抛出错误，未定义函数或方法 'fetch' 用于类型为 'struct' 的输入参数."

I am trying to import tables to my MATLAB workspace and it keeps throwing me an error, "Undefined function or method 'fetch' for input arguments of type 'struct'."

这是我正在尝试执行的代码:

This is my code that i am trying to execute:

dyn_conformer = exec(conn, 'SELECT * FROM dyn_conformer'); 
rs =fetch(dyn_conformer);

当我在工作区中打开对象时，它指出它是无效或关闭的连接".但是，以前我设法导入其他表，它似乎执行得很好(它们存储为游标对象).突然之间，它对我尝试导入的其他表抛出错误.

When i opened the object in the workspace, it stated that it was "Invalid or closed connection". However, previously i manage to import other tables and it seemed to execute perfectly (they are stored as a cursor object). All of a sudden, its throwing an error for other tables that i am trying to import.

我已连接到数据库，conn = database('postgres','username','password','org.postgresql.Driver','jdbc:postgresql://localhost:5433/postgres');.

推荐答案

我建议您在运行 exec 之前检查是否存在连接变量，并且它是正确建立的连接.你可以这样做:

I would recommend you to check for existing of connection variable and that it is the properly established connection before running exec. You can do it like this:

if ~exist('conn','var') || ~isconnection(conn)
    conn = database('postgres','username','password','org.postgresql.Driver',...
           'jdbc:postgresql://localhost:5433/postgres');
else
    dyn_conformer = exec(conn, 'SELECT * FROM dyn_conformer'); 
    rs =fetch(dyn_conformer);
end

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