Select 在 MYSQL — Select 所有记录

Question

I have a function like below:

public function select($id=null) {
    $query = "select * from press_releases where id = {$id}";

    $results = $this->db->query($query);

    return $results;
}

If no $id is specified during function invoke, I want to return all the records but I think NULL default value is not a good option for that. What should I do instead of NULL to retrieve all the records other than using a another query which doesn't specify the id field in the where section.

Thanks...

Answer 1

$query = "select * from press_releases";
if (!empty($id))
{
   $query .= "where id = {$id}";
}

If $id is an integer, I would use:

$id = (int) $id;
if ($id > 0)
...

Either way I would make sure $id is safe to use.

Answer 2

This may work:

$query = "select * from press_releases where id = {$id} OR {$id} IS NULL";

Answer 3

You could replace the where operator to LIKE, as in

$query = "select * from press_releases where id LIKE '{$id}'";

and change the default value to the '%', but I don't like this solution for efficiency reasons.

You should do that only if you absolutely need to keep the query as you written. Otherwise change the query to append the where condition only if the $id parameter is given. That would be the right solution.

Answer 4

SELECT DISTINCT id FROM press_releases