如何从CodeIgniter中的失败数据库查询中恢复？

Question

In CodeIgniter, if your sql query fails, then the script stops running and you get an error. Is there any way to do it so you can try a query, and if it fails, then you silently detect it and try a different query without the user knowing that the query failed?

Answer 1

You could modify the Exceptions class to... throw an exception. Just create MY_Exceptions.php in application/core/ :

class MY_Exceptions extends CI_Exceptions {

    function show_error($heading, $message, $template = 'error_general', $status_code = 500)
    {
        // BEGIN EDIT
        if ($template === 'error_db')
        {
            throw new Exception(implode("\n", (array) $message));
        }
        // END EDIT

        set_status_header($status_code);

        $message = '<p>'.implode('</p><p>', ( ! is_array($message)) ? array($message) : $message).'</p>';

        if (ob_get_level() > $this->ob_level + 1)
        {
            ob_end_flush();
        }
        ob_start();
        include(APPPATH.'errors/'.$template.'.php');
        $buffer = ob_get_contents();
        ob_end_clean();
        return $buffer;
    }
}

Then use a try/catch block to check for the error and attempt to run another query:

try {
    $this->db->get('table1');
} catch (Exception $e) {
    $this->db->get('table2');
}

It's kind of a sloppy workaround, but it gets the job done.

You might want to take a look at transactions as well:

Running Transactions

To run your queries using transactions you will use the $this->db->trans_start() and $this->db->trans_complete() functions as follows:

$this->db->trans_start();
$this->db->query('AN SQL QUERY...');
$this->db->query('ANOTHER QUERY...');
$this->db->query('AND YET ANOTHER QUERY...');
$this->db->trans_complete();

You can run as many queries as you want between the start/complete functions and they will all be committed or rolled back based on success or failure of any given query.

Answer 2

One of the ways to achieve this is

First.

Set  ['db_debug'] = FALSE; in config/database.php

Then,

In your model -

public function attempt_one($data) {
  //build your query ....
  $query_result = $this->db->insert('table_name');

  if(!$query_result) {
     $this->error = $this->db->_error_message();
     $this->errorno = $this->db->_error_number();
     return false;
  }
  return $something;
}

public function attempt_two() {
  //another query goes in here ...
}

in your controller -

public function someAction ()
{
  //some code 
  $data = $some_data;
  $result1 = $this->yourmodel->attempt_one($data);
  if($result1 === false)
  {
    //Some code to send an email alert that first query failed with error message 
    //and/or log the error message/ number 
    $result2 = $this->yourmodel->attempt_two($data);
  }

}

Answer 3

Just use

$this->db->simple_query() 

rather than

$this->db->query()

Simple Query will return true/false.

Answer 4

您可以使用以下方法访问数据库

• $this->db->_error_message();
• $this->db->_error_number();

Answer 5

您可以从他们的官方论坛中查看此主题，讨论并建议针对此特定主题的解决方案： http ： //codeigniter.com/forums/viewthread/76524/