It should be noted that the primary_key member variable is only set to 1 if the primary key on the table is only on that 1 field. If you have a table that has a multiple column primary key, then you will not get what you might expect.
For example:
CREATE TABLE `line_item_table` (
`liForeignKey1` int(11) unsigned not null,
`liForeignKey2` int(11) unsigned not null,
PRIMARY KEY (`liForeignKey1`, `liForeignKey2`)
) ENGINE=MyISAM;
While you might expect that primary_key == 1 for both columns; var_dump() will show you that you get the following for both fields:
["primary_key"]=>int(0)
This is as of PHP 5.2.13 and MySQL 5.0.51
mysql_fetch_field
(PHP 4, PHP 5)
mysql_fetch_field — Obtém informações sobre uma coluna de um resultado e retorna como um objeto
Descrição
mysql_fetch_field
( resource
$result
, int $field_offset = ?
) : objectRetorna um objeto contendo informações sobre o campo. Esta função pode ser usada para obter informações sobre os campos de um resultado de uma consulta.
Parâmetros
-
result -
O resultado tipo resource que está sendo avaliado. Esse resultado é original de uma chamada a mysql_query().
-
field_offset -
O índice numérico do campo. Se o índice não for especificado, o próximo campo que não tenha sido obtido por esta função é retornado. O parâmetro
field_offsetcomeça em0.
Valor Retornado
Retorna um object contendo a informação sobre o campo. As propriedades do objeto são:
- name - nome da coluna
- table - a tabela a qual o objeto pertence
- def - o valor padrão da coluna
- max_length - o limite de tamanho da coluna
-
not_null - 1 se a coluna não puder ser
null - primary_key - 1 se a coluna é a chave primária
- unique_key - 1 se a coluna é a chave única
- multiple_key - 1 se a coluna é uma chave não-única
- numeric - 1 se a coluna é numérica
- blob - 1 se a coluna é um BLOB
- type - o tipo da coluna
- unsigned - 1 se a coluna é sem sinal
- zerofill - 1 se a coluna é prenchida com zero
Exemplos
Exemplo #1 Exemplo mysql_fetch_field()
<?php
$conn = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$conn) {
die('Não foi possível conectar: ' . mysql_error());
}
mysql_select_db('database');
$result = mysql_query('select * from table');
if (!$result) {
die('A consulta falhou: ' . mysql_error());
}
/* obtém as informações da coluna */
$i = 0;
while ($i < mysql_num_fields($result)) {
echo "Informação para a coluna $i:<br />\n";
$meta = mysql_fetch_field($result, $i);
if (!$meta) {
echo "Sem informação disponível<br />\n";
}
echo "<pre>
blob: $meta->blob
max_length: $meta->max_length
multiple_key: $meta->multiple_key
name: $meta->name
not_null: $meta->not_null
numeric: $meta->numeric
primary_key: $meta->primary_key
table: $meta->table
type: $meta->type
default: $meta->def
unique_key: $meta->unique_key
unsigned: $meta->unsigned
zerofill: $meta->zerofill
</pre>";
$i++;
}
mysql_free_result($result);
?>
Notas
Nota: Nomes de campos nesta função diferenciam maiúsculas e minusculas.
add a note
User Contributed Notes 13 notes
Jonathan ¶
13 years ago
david at vitam dot be ¶
15 years ago
A little function to help coders to distinct the tablename from a multiselect query where some fields has the same name in differents tables.
<?php
public function sql($sql) {
$T_Return=array();
$result=@mysql_query($sql);
$i=0;
while ($i < mysql_num_fields($result)) {
$fields[]=mysql_fetch_field($result, $i);
$i++;
}
while ($row=mysql_fetch_row($result)) {
$new_row=array();
for($i=0;$i<count($row); $i++) {
$new_row[ $fields[$i]->table][$fields[$i]->name]=$row[$i];
}
$T_Return[]=$new_row;
}
return $T_Return;
}
?>
Nick Baicoianu ¶
18 years ago
Be sure to note that $max_length is the length of the longest value for that field in the returned dataset, NOT the maximum length of data that column is designed to hold.
krang at krang dot org dot uk ¶
22 years ago
The field type returns what PHP classifies the data found in the field, not how it is stored in the database; use the following example to retrieve the MySQL information about the field....
<?php
$USERNAME = '';
$PASSWORD = '';
$DATABASE = '';
$TABLE_NAME = '';
mysql_connect('localhost', $USERNAME, $PASSWORD)
or die ("Could not connect");
$result = mysql_query("SHOW FIELDS FROM $DATABASE.$TABLE_NAME");
$i = 0;
while ($row = mysql_fetch_array($result)) {
echo $row['Field'] . ' ' . $row['Type'];
}
?>
jorachim at geemail dot com ¶
15 years ago
If you want the fields in a table, a simple DESCRIBE query will work:
<?php
$query ="DESCRIBE Users";
$result = mysql_query($query);
echo "<ul>";
while($i = mysql_fetch_assoc($result))
echo "<li>{$i['Field']}</li>";
echo "</ul>";
?>
Should do the trick.
Daniel B ¶
12 years ago
Simple function to display all data in a query...
function dumpquery($query) {
$numfields = mysql_num_fields($query);
echo '<table border="1" bgcolor="white"><tr>';
for ($i = 0; $i<$numfields; $i += 1) {
$field = mysql_fetch_field($query, $i);
echo '<th>' . $field->name . '</th>';
}
echo '</tr>';
while ($fielddata = mysql_fetch_array($query)) {
echo '<tr>';
for ($i = 0; $i<$numfields; $i += 1) {
$field = mysql_fetch_field($query, $i);
echo '<td>' . $fielddata[$field->name] . '</td>';
}
echo '</tr>';
}
echo '</table>';
}
lucien at ocia dot nl ¶
12 years ago
Performance Notes!
I used this script for testing, the table has 26 colums.
<?php
$t_start = microtime(true);
$sql = mysql_query("SELECT * FROM `table` LIMIT 1") or trigger_error(mysql_error(), E_USER_WARNING);
for ($i = 0; $i < mysql_num_fields($sql); $i++) {
$meta = mysql_fetch_field($sql, $i);
echo "Information for column ".$meta->name.":\n";
echo
"\tblob: $meta->blob
\tmax_length: $meta->max_length
\tmultiple_key: $meta->multiple_key
\tname: $meta->name
\tnot_null: $meta->not_null
\tnumeric: $meta->numeric
\tprimary_key: $meta->primary_key
\ttable: $meta->table
\ttype: $meta->type
\tunique_key: $meta->unique_key
\tunsigned: $meta->unsigned
\tzerofill: $meta->zerofill
";
}
$t_stop = microtime(true);
$t_proc = $t_stop - $t_start;
echo "processing time query 1: ".number_format($t_proc * 1000, 3)." ms\n";
unset($t_start);
unset($t_stop);
unset($t_proc);
$t_start = microtime(true);
$sql = mysql_query("DESCRIBE `table`");
while ($res = mysql_fetch_array($sql, MYSQL_ASSOC)) {
print_r($res);
}
$t_stop = microtime(true);
$t_proc = $t_stop - $t_start;
echo "processing time query 2: ".number_format($t_proc * 1000, 3)." ms\n";
?>
Query 1 => 0.444 ms
Query 2 => 1.146 ms
So for easy usage, Query 2 is advised... But if your a performance-geek, you should use Query 1.
php [spat] hm2k.org ¶
15 years ago
An improvement on the earlier mysql_column_exists function.
<?php
function mysql_column_exists($table_name, $column_name, $link=false) {
$result = @mysql_query("SHOW COLUMNS FROM $table_name LIKE '$column_name'", $link);
return (mysql_num_rows($result) > 0);
}
?>
mwwaygoo AT hotmail DOT com ¶
11 years ago
Using mysql_fetch_field you can produce a more robust version of mysql_fetch_assoc.
When querying 2 tables with the same field names, generally you would need to use mysql_fetch_row to get an integer key'ed array rather than an associated key'ed array. This is because fields of the same name in the second table will over-write the data returned from the first table.
However this simple function will insert the table name prior to the field name for the key and prevent cross-overs.
ie SELECT *, 'test' AS test 4 FROM table AS T_1, table AS T_2 WHERE T_1.a=T_2.b
could produce:
mysql_fetch_assoc() returns
array(
'index'=>2,
'a'=>'pear',
'b'=>'apple',
'test'=>'test',
4=>4
)
mysql_fetch_table_assoc() returns
array(
'T_1.index' =>1,
'T_1.a'=>'apple',
'T_1.b'=>'banana',
'T_2.index'=>2,
'T_2.a'=>'pear',
'T_2.b'=>'apple',
'test'=>'test',
4=>4
)
<?php
function mysql_fetch_table_assoc($resource)
{
// function to get all data from a query, without over-writing the same field
// by using the table name and the field name as the index
// get data first
$data=mysql_fetch_row($resource);
if(!$data) return $data; // end of data
// get field info
$fields=array();
$index=0;
$num_fields=mysql_num_fields($resource);
while($index<$num_fields)
{
$meta=mysql_fetch_field($resource, $index);
if(!$meta)
{
// if no field info then just use index number by default
$fields[$index]=$index;
}
else
{
$fields[$index]='';
// deal with field aliases - ie no table name (SELECT T_1.a AS temp)
if(!empty($meta->table)) $fields[$index]=$meta->table.'.';
// deal with raw data - ie no field name (SELECT 1)
if(!empty($meta->name)) $fields[$index].=$meta->name; else $fields[$index].=$index;
}
$index++;
}
$assoc_data=array_combine($fields, $data);
return $assoc_data;
}
?>
TALU ¶
15 years ago
XML generation.
Bit of a security risk allowing parameters to select db and table on live server (unless user is restricted or replace the $_GET with fixed value.)
Outputs xml with standard format for <config> part to generate forms in flash.
<?php
//
// makeXML.php?db=dbname&table=tablename
//
set_time_limit(300);
$host = "localhost";
$user = "root";
$password = "root";
$database = $_GET['db'];
$table = $_GET['table'];
mysql_connect($host,$user,$password);
@mysql_select_db($database) or die( "Unable to select database");
$querytext="SELECT * FROM ".$table;
$result=mysql_query($querytext);
if ($result){
$num=mysql_num_rows($result);
}else{
$num=0;
}
?>
<?php
header('Content-Type: text/xml');
echo "<?xml version='1.0'?>";
if ($num > 0){
?>
<<?php echo $table?>>
<config>
<?php
// Display number of fields
echo "<numFields>".mysql_num_fields($result)."</numFields>";
$i = 0;
$primaryKey = "";
$nameArray = array();
$maxLengthArray = array();
$typeArray = array();
while ($i < mysql_num_fields($result)) {
$meta = mysql_fetch_field($result, $i);
$nameArray[$i] = $meta->name;
$maxLengthArray[$i] = $meta->max_length;
$typeArray[$i] = $meta->type;
if ($meta->primary_key){
$primaryKey = $meta->name;
}
$i++;
}
$i = 0;
echo "<fieldNames>";
while ($i < count($nameArray)) {
echo "<field".$i.">".$nameArray[$i]."</field".$i.">";
$i++;
}
echo "</fieldNames>";
$i = 0;
echo "<fieldMaxLength>";
while ($i < count($maxLengthArray)) {
echo "<field".$i.">".$maxLengthArray[$i]."</field".$i.">";
$i++;
}
echo "</fieldMaxLength>";
$i = 0;
echo "<fieldType>";
while ($i < count($typeArray)) {
echo "<field".$i.">".$typeArray[$i]."</field".$i.">";
$i++;
}
echo "</fieldType>";
?>
<primaryKey><?php echo $primaryKey?></primaryKey>
<numRecords><?php echo $num?></numRecords>
</config>
<?php
$i=0;
while ($i < $num) {
$ID=mysql_result($result,$i,"ID");
$value=mysql_result($result,$i,"value");
$title=mysql_result($result,$i,"title");
$description=mysql_result($result,$i,"description");
?>
<row>
<ID><?php echo $ID?></ID>
<weighting><?php echo $value?></weighting>
<title><?php echo $title?></title>
<description><?php echo $description?></description>
</row>
<?php
$i = $i + 1;
}
?>
</<?php echo $table?>>
<?php
}
?>
php at brayra dot com ¶
22 years ago
I needed to get the field information and the enum/set values. Here is the function I created to expand the object returned by mysql_fetch_field. I also, decided to return all the fields for a table in an array of field objects by "name" and position much like mysql_fetch_array does.
You could test it by using:
<?php
$myfields = GetFieldInfo('test_table');
print "<pre>";
print_r($myfields);
print "</pre>";
?>
The field objects now have 'len', 'values' and 'flags' parameters.
NOTE: 'values' only has data for set and enum fields.
<?php
//This assumes an open database connection
//I also use a constant DB_DB for current database.
function GetFieldInfo($table)
{
if($table == '') return false;
$fields = mysql_list_fields(DB_DB, $table);
if($fields){
$columns = mysql_query('show columns from ' . $table);
if($columns){
$num = mysql_num_fields($fields);
for($i=0; $i < $num; ++$i){
$column = mysql_fetch_array($columns);
$field = mysql_fetch_field($fields, $i);
$flags = mysql_field_flags($fields, $i);
if($flags == '') $flags=array();
else $flags = explode(' ',$flags);
if (ereg('enum.(.*).',$column['Type'],$match))
$field->values = explode(',',$match[1]);
if (ereg('set.(.*).',$column['Type'],$match))
$field->values = explode(',',$match[1]);
if(!$field->values) $field->values = array();
$field->flags = $flags;
$field->len = mysql_field_len($fields, $i);
$result_fields[$field->name] = $field;
$result_fields[$i] = $field;
}
mysql_free_result($columns);
}
mysql_free_result($fields);
return $result_fields;
}
return false;
}
?>
hope someone else finds this useful.
eviltofu at gmail dot com ¶
12 years ago
MYSQLI_TYPE_BLOB indicates the field is a BLOB or a TEXT. I think you would need to check the blob value. If its true then it's a BLOB, otherwise it's a TEXT. Can someone confirm?
dheep ¶
15 years ago
Simple PHP script for displaying the field names. Presuming the database is seleected already.
<?php
$sql = "SELECT * FROM table_name;";
$result = mysql_query($sql);
$i = 0;
while($i<mysql_num_fields($result))
{
$meta=mysql_fetch_field($result,$i);
echo $i.".".$meta->name."<br />";
$i++;
}
?>
OUTPUt:
0.id
1.todo
2.due date
3.priority
4.type
5.status
6.notes
hope this is useful.
