MySQL新行没有插入默认值

Question

ALTER TABLE  `songs`
CHANGE  `artist_name`  `artist_name` VARCHAR( 255 ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL DEFAULT  'N/A'

^ So that's my table and the default for artist_name is 'N/A'. I'm using a form to submit data. However, when I submit the data through a form, the row doesn't contain 'N/A' and the value is empty. Anyone know what is going on?

$video_id=$_POST['video_id'];
$song_name=$_POST['song_name'];
$artist_name=$_POST['artist_name'];
$movie_name=$_POST['movie_name'];
$language=$_POST['language'];
$oldornew=$_POST['oldornew'];

//inserting data order
$order = "INSERT INTO dhb_dhb.songs
        (video_id, song_name,artist_name, movie_name,language,oldornew)
        VALUES
        ('$video_id', '$song_name','$artist_name', '$movie_name', '$language', '$oldornew')";

Answer 1

You'd have to unset the specific $_POST key if it's empty, so NULL will be inserted which then automatically is assigned the default value. Now you're just inserting a blank string, which is not translated into the default column value, since it isn't NULL .

EDIT The easiest way to do it then is to use an associative array, containing only the keys/values that are not empty:

$data = array('video_id' => $video_id);
foreach(array('artist_name', 'song_name') as $key)
    if(!empty($_POST[$key])){
        $data[$key] = mysql_real_escape_string($key);
    }
}

$columns = "`". implode("`, `", array_keys($data)) ."`";
$values = "'". implode("', '", array_values($data)) ."'";
$query = "INSERT INTO table ({$columns}) VALUES ({$values})";

This hasn't been tested and values should be tested before inserting (eg is $song_id really an integer?) but this is the general idea.

Answer 2

Any user input can be checked to see if it's set, and if not, use a default value of NULL:

$variable = (!empty($_POST['variable'])) ? $_POST['variable'] : NULL;

Now calling this in a query will set the default value if $_POST['variable'] is empty (or unset).

I must caution. Whenever you take user input and put directly into a Database Query as you've done in your code example, you're opening up a serious security vulnerability known as SQL Injection . Consider sanitizing your user input using mysql_real_escape_string

EDIT:

Your code could then be applied by using something like the following:

<?php

$data = array(
    'video_id',
    'song_name',
    'artist_name',
    'movie_name',
    'language',
    'oldornew',
);
$insert_ary = array();

foreach ($data as $val) {
    if (!empty($_POST[$val])) {
        $insert_ary[$val] = mysql_real_escape_string($_POST[$val]);
    }
}

$columns = implode(', ', array_keys($insert_ary));
$values = implode("', '", $insert_ary);
$sql = "INSERT INTO dhb_dhb.songs ($columns) VALUES('$values')";