mysql_fetch_field

(PHP 3, PHP 4, PHP 5)

mysql_fetch_field --  从结果集中取得列信息并作为对象返回

说明

object mysql_fetch_field ( resource result [, int field_offset] )

返回一个包含字段信息的对象。

mysql_fetch_field() 可以用来从某个查询结果中取得字段的信息。如果没有指定字段偏移量,则下一个尚未被 mysql_fetch_field() 取得的字段被提取。

对象的属性为:

  • name - 列名

  • table - 该列所在的表名

  • max_length - 该列最大长度

  • not_null - 1,如果该列不能为 NULL

  • primary_key - 1,如果该列是 primary key

  • unique_key - 1,如果该列是 unique key

  • multiple_key - 1,如果该列是 non-unique key

  • numeric - 1,如果该列是 numeric

  • blob - 1,如果该列是 BLOB

  • type - 该列的类型

  • unsigned - 1,如果该列是无符号数

  • zerofill - 1,如果该列是 zero-filled

注: 本函数返回的字段名是区分大小写的。

例子 1. mysql_fetch_field()

<?php
mysql_connect
('localhost:3306', $user, $password)
    or die(
"Could not connect: " . mysql_error());
mysql_select_db("database");
$result = mysql_query("select * from table")
    or die(
"Query failed: " . mysql_error());
/* get column metadata */
$i = 0;
while (
$i < mysql_num_fields($result)) {
    echo
"Information for column $i:<br />\n";
    
$meta = mysql_fetch_field($result);
    if (!
$meta) {
        echo
"No information available<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
unique_key:   $meta
->unique_key
unsigned:     $meta
->unsigned
zerofill:     $meta
->zerofill
</pre>"
;
    
$i++;
}
mysql_free_result($result);
?>

参见 mysql_field_seek()


add a note add a note User Contributed Notes
inaxio
04-Nov-2005 11:34
just another option to get all enum|set values from table definition. values are stored into arrays using the same field name

$result = mysql_query("SHOW COLUMNS FROM [table_name]");
while($row = mysql_fetch_object($result)){
   if(ereg(('set|enum'), $row->Type)){
       eval(ereg_replace('set|enum', '$'.$row->Field.' = array', $row->Type).';');
   }
}
Nick Baicoianu
16-Sep-2005 02:18
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.
admin at str-atm dot com
13-Sep-2005 01:15
If you need to get separated field size you should use
this part of code (I also included a database request function):

!!!!! Take care of warped lines

----------------
// Function to call to perform a database request

<?
function sql_request($sql_query,$db_name)
  {
   global
$rows_count;
  
$db_link = mysql_connect("localhost","username","password")
or die(
"MySQL connect failed");
   @
mysql_select_db($db_name) or
die(
"unable to select: $db_name");
  
$query_answer = mysql_query($sql_query);
  
$rows_count = mysql_num_rows($query_answer);
  
mysql_close($db_link);
   return
$query_answer;
  }

$editing_db = "mydb";
$editing_table = "mytable";

$query_answer = sql_request("SHOW FIELDS FROM $editing_table",$editing_db);
$i = 0;
while (
$row = mysql_fetch_array($query_answer))
{
 
$table_structure[$i][0] = $row['Field'];
 
$first_parenthesis = strpos($row['Type'],"(");
 
$last_parenthesis = strpos($row['Type'],")");
  if (
$first_parenthesis AND $last_parenthesis)
  {
  
$table_structure[$i][1] = substr($row['Type'],0,$first_parenthesis);
  
$table_structure[$i][2] = substr($row['Type'],$first_parenthesis+1,
$last_parenthesis-$first_parenthesis-1);
  }
  if (
$row[Key] == "PRI") $table_structure[$i][3] = 1;
  echo
$i." ".$table_structure[$i][0]." ";
  echo
$table_structure[$i][1]." ";
  echo
$table_structure[$i][2]." ".$table_structure[$i][3]."<br>";
 
$i++;
}
?>
Hope this will be usefull!

Andre Lebeuf
STR ATM and Terminals
cortalux at gmail dot com
24-Jun-2005 01:09
A far easier way of getting information upon an enum field, is this.

function enumget($field="",$table="") {
   $result=mysql_query("SHOW COLUMNS FROM `$table` LIKE '$field'");
   if(mysql_num_rows($result)>0){
       $row=mysql_fetch_row($result);
       $options=explode("','", preg_replace("/(enum|set)\('(.+?)'\)/","\\2", $row[1]));
   } else {
       $options=array();
   }
   return $options;
}
creak at foolstep dot com
18-Jul-2003 06:26
Sorry, the last pattern doesn't work with type whithout length, so it would be better if you change it with this one :
   "^([a-zA-Z]+)\(?([^\)]*)\)?$"

It's still $type[1] for the type and $type[2] for the length.

Creak
blakjak at nospam dot com
27-Mar-2003 06:18
mysql_fetch_field will fail if your result set's internal pointer has advanced past the end of the result.

So, if you use ...

$result = mysql_query("select * from person where id=1"); // returns 1 row
$row = mysql_fetch_row($result);

while($field = mysql_fetch_field){
 echo $field->name;
}

... you won't see any fields.  If you need to use mysql_fetch_field, you need to do it before you've iterated through all the rows in the result set.
kflam at awc dot net dot au
19-Jun-2002 11:56
#Input: the table name and the enum field
#Output: an array that stores all options of the enum field or
#false if the input field is not an enum
function getEnumOptions($table, $field) {
   $finalResult = array();

   if (strlen(trim($table)) < 1) return false;
   $query  = "show columns from $table";
   $result = mysql_query($query);
   while ($row = mysql_fetch_array($result)){
       if ($field != $row["Field"]) continue;
       //check if enum type
       if (ereg('enum.(.*).', $row['Type'], $match)) {
           $opts = explode(',', $match[1]);
           foreach ($opts as $item)
               $finalResult[] = substr($item, 1, strlen($item)-2);
       }
       else
               return false;
   }
   return $finalResult;
}

The function could be handy when making a selection option without typing all the options items respectively.
chrisshaffer at bellsouth dot net
07-Jun-2002 02:22
Slight error in the above comment:
$fieldLen = split("','",substr(1,-1,$fieldLen));

should read:
$fieldLen = split("','",substr($fieldLen,1,-1));

oops! ;)

I did take the above code (which saved me at least two hours worth of work), and massaged it into a function:

function mysql_enum_values($tableName,$fieldName)
{
  $result = mysql_query("DESCRIBE $tableName");

  //then loop:
  while($row = mysql_fetch_array($result))
  {
   //# row is mysql type, in format "int(11) unsigned zerofill"
   //# or "enum('cheese','salmon')" etc.

   ereg('^([^ (]+)(\((.+)\))?([ ](.+))?$',$row['Type'],$fieldTypeSplit);
   //# split type up into array
   $ret_fieldName = $row['Field'];
   $fieldType = $fieldTypeSplit[1];// eg 'int' for integer.
   $fieldFlags = $fieldTypeSplit[5]; // eg 'binary' or 'unsigned zerofill'.
   $fieldLen = $fieldTypeSplit[3]; // eg 11, or 'cheese','salmon' for enum.

   if (($fieldType=='enum' || $fieldType=='set') && ($ret_fieldName==$fieldName) )
   {
     $fieldOptions = split("','",substr($fieldLen,1,-1));
     return $fieldOptions;
   }
  }

  //if the funciton makes it this far, then it either
  //did not find an enum/set field type, or it
  //failed to find the the fieldname, so exit FALSE!
  return FALSE;

}

The most useful thing that I can think to do with this is to populate a HTML Dropdown box with it:

echo "<SELECT NAME=\"Select\" SIZE='1'>";
foreach($fieldOptions as $tmp)
{
  echo "<OPTION>$tmp";
}

Hope this helps  :D
justin at quadmyre dot com
19-Apr-2002 08:00
Same problem, slightly different solution.

$result = mysql_query("DESCRIBE tablename");
# or SHOW COLUMNS FROM
# or SHOW FIELDS FROM

then loop:

$row = mysql_fetch_array($result);
# row is mysql type, in format "int(11) unsigned zerofill"
# or "enum('cheese','salmon')" etc.

ereg('^([^ (]+)(\((.+)\))?([ ](.+))?$',$row['Type'],$fieldTypeSplit);
# split type up into array

$fieldType = $fieldTypeSplit[1]; # eg 'int' for integer.
$fieldFlags = $fieldTypeSplit[5]; # eg 'binary' or 'unsigned zerofill'.
$fieldLen = $fieldTypeSplit[3]; # eg 11, or 'cheese','salmon' for enum.

You might then like to:

if ($fieldType=='enum' or $fieldType=='set')
  $fieldLen = split("','",substr(1,-1,$fieldLen));

So for enum or set types, $fieldLen becomes an array of possible values.

Hope that helps someone out there...
php at brayra dot com
22-Mar-2002 08:09
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:
$myfields = GetFieldInfo('test_table');
print "<pre>";
print_r($myfields);
print "</pre>";

The field objects now have 'len', 'values' and 'flags' parameters.
NOTE: 'values' only has data for set and enum fields.

//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.
krang at krang dot org dot uk
10-Mar-2002 10:12
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....

$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'];
}
dave at techweavers dot net
04-Oct-2000 04:48
If you want to get the max length of a column not just the data use this:
$result = mysql_query ("SELECT * FROM table");
$fields = mysql_num_fields ($result);
$i = 0;
while ($i < $fields) {
$len  = mysql_field_len  ($result, $i);
$i++;
}
Or refer to http://www.php.net/manual/function.mysql-field-type.php