mysqli_result::fetch_field_direct

mysqli_fetch_field_direct

(PHP 5, PHP 7, PHP 8)

mysqli_result::fetch_field_direct -- mysqli_fetch_field_direct — Obtener los metadatos de un único campo

Descripción

Estilo orientado a objetos

mysqli_result::fetch_field_direct(int $fieldnr): object

Estilo por procedimientos

mysqli_fetch_field_direct(mysqli_result $result, int $fieldnr): object

Devuelve un objeto que contiene la información de definición de un campo del conjunto de resultados especificado.

Parámetros

result: Sólo estilo por procedimientos: Un conjunto de identificadores de resultados devuelto por mysqli_query(), mysqli_store_result() o mysqli_use_result().
fieldnr: El número de campo. Este valor debe estar en un rango desde 0 a número de campos - 1.

Valores devueltos

Devuelve un objeto que contiene la información de definición del campo o false si no está disponible la información del campo especificada por fieldnr.

**Atributos del objeto**
Atributo	Descripción
name	El nombre de la columna
orgname	El nombre original de la columna si se especificó un alias
table	El nombre de la tabla al que pertenece el campo (si no es calculado)
orgtable	El nombre original de la tabla si se especificó un alias
def	El valor predeterminado de este campo, representado como una cadena
max_length	El ancho máximo del campo del conjunto de resultados.
length	El ancho del campo, como fue especificado en la definición de la tabla.
charsetnr	El número del conjunto de caracteres del campo.
flags	Un entero que representa las banderas de bits del campo.
type	El tipo de datos usado por el campo
decimals	El número de decimales empleados (para campos numéricos)

Ejemplos

Ejemplo #1 Estilo orientado a objetos

<?php
$mysqli = new mysqli("localhost", "mi_usuario", "mi_contraseña", "world");

/* comprobar la conexión */
if (mysqli_connect_errno()) {
    printf("Falló la conexión: %s\n", mysqli_connect_error());
    exit();
}

$consulta = "SELECT Name, SurfaceArea from Country ORDER BY Name LIMIT 5";

if ($resultado = $mysqli->query($consulta)) {

    /* Obtener la información del campo para la columna 'SurfaceArea' */
    $info_campo = $resultado->fetch_field_direct(1);

    printf("Nombre:        %s\n", $info_campo->name);
    printf("Tabla:         %s\n", $info_campo->table);
    printf("Longitud máx.: %d\n", $info_campo->max_length);
    printf("Banderas:      %d\n", $info_campo->flags);
    printf("Tipo:          %d\n", $info_campo->type);

    $resultado->close();
}

/* cerrar la conexión */
$mysqli->close();
?>

Ejemplo #2 Estilo por procedimientos

<?php
$enlace = mysqli_connect("localhost", "mi_usuario", "mi_contraseña", "world");

/* comprobar la conexión */
if (mysqli_connect_errno()) {
    printf("Falló la conexión: %s\n", mysqli_connect_error());
    exit();
}

$consulta = "SELECT Name, SurfaceArea from Country ORDER BY Name LIMIT 5";

if ($resultado = mysqli_query($enlace, $consulta)) {

    /* Obtener la información del campo para la columna 'SurfaceArea' */
    $info_campo = mysqli_fetch_field_direct($resultado, 1);

    printf("Nombre:     %s\n", $info_campo->name);
    printf("Tabla:    %s\n", $info_campo->table);
    printf("Longitud máx.: %d\n", $info_campo->max_length);
    printf("Banderas:    %d\n", $info_campo->flags);
    printf("Tipo:     %d\n", $info_campo->type);

    mysqli_free_result($resultado);
}

/* cerrar la conexión */
mysqli_close($enlace);
?>

El resultado de los ejemplos sería:

Nombre:        SurfaceArea
Tabla:         Country
Longitud máx.: 10
Banderas:      32769
Tipo:          4

Ver también

mysqli_num_fields() - Obtiene el número de campos de un resultado
mysqli_fetch_field() - Retorna el próximo campo del resultset
mysqli_fetch_fields() - Devuelve un array de objetos que representan los campos de un conjunto de resultados

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User Contributed Notes 12 notes

down

daniel at summit cove dot com ¶

15 years ago

Here's a bigger list of data types.  I got this by creating every type I could and calling fetch_fields():

<?php
$mysql_data_type_hash = array(
    1=>'tinyint',
    2=>'smallint',
    3=>'int',
    4=>'float',
    5=>'double',
    7=>'timestamp',
    8=>'bigint',
    9=>'mediumint',
    10=>'date',
    11=>'time',
    12=>'datetime',
    13=>'year',
    16=>'bit',
    //252 is currently mapped to all text and blob types (MySQL 5.0.51a)
    253=>'varchar',
    254=>'char',
    246=>'decimal'
);
?>

down

ben dot NOSPAM at NOSPAM dot seraphire dot com ¶

11 years ago

This may be obvious, but the constants for the field types are already defined in PHP, and can be found in the documentation at: http://php.net/manual/en/mysqli.constants.php

down

cjs at ashdowntech dot com ¶

16 years ago

According to
http://www.redferni.uklinux.net/mysql/MySQL-Protocol.html

Data type values are:

DECIMAL           0       ENUM           247
TINY              1       SET            248
SHORT             2       TINY_BLOB      249
LONG              3       MEDIUM_BLOB    250
FLOAT             4       LONG_BLOB      251
DOUBLE            5       BLOB           252
NULL              6       VAR_STRING     253
TIMESTAMP         7       STRING         254
LONGLONG          8       GEOMETRY       255
INT24             9
DATE             10
TIME             11
DATETIME         12
YEAR             13
NEWDATE          14

Note that this is not tested and does not contain
all the values noted by deluxmozart

down

cjs at ashdowntech dot com ¶

16 years ago

According to
dev.mysql.com/sources/doxygen/mysql-5.1/mysql__com_8h-source.html
the flag bits are:
 
 NOT_NULL_FLAG          1         /* Field can't be NULL */
 PRI_KEY_FLAG           2         /* Field is part of a primary key */
 UNIQUE_KEY_FLAG        4         /* Field is part of a unique key */
 MULTIPLE_KEY_FLAG      8         /* Field is part of a key */
 BLOB_FLAG             16         /* Field is a blob */
 UNSIGNED_FLAG         32         /* Field is unsigned */
 ZEROFILL_FLAG         64         /* Field is zerofill */
 BINARY_FLAG          128         /* Field is binary   */
 ENUM_FLAG            256         /* field is an enum */
 AUTO_INCREMENT_FLAG  512         /* field is a autoincrement field */
 TIMESTAMP_FLAG      1024         /* Field is a timestamp */

down

andre at koethur dot de ¶

10 years ago

Here are two methods for converting the 'type' and 'flags' attributes to text for debugging purposes. They both use the predefined MYSQLI_ constants to generate the text.

<?php

public static function h_type2txt($type_id)
{
    static $types;

    if (!isset($types))
    {
        $types = array();
        $constants = get_defined_constants(true);
        foreach ($constants['mysqli'] as $c => $n) if (preg_match('/^MYSQLI_TYPE_(.*)/', $c, $m)) $types[$n] = $m[1];
    }

    return array_key_exists($type_id, $types)? $types[$type_id] : NULL;
}

public static function h_flags2txt($flags_num)
{
    static $flags;

    if (!isset($flags))
    {
        $flags = array();
        $constants = get_defined_constants(true);
        foreach ($constants['mysqli'] as $c => $n) if (preg_match('/MYSQLI_(.*)_FLAG$/', $c, $m)) if (!array_key_exists($n, $flags)) $flags[$n] = $m[1];
    }

    $result = array();
    foreach ($flags as $n => $t) if ($flags_num & $n) $result[] = $t;
    return implode(' ', $result);
}

?>

down

gmx dot net at Hoffmann dot P ¶

10 years ago

Warning!
This function is not only more memory consuming than expected but the consumption also depends on the size of the result set. So if you realy only want to get your field_names you might want to append " LIMIT 1" or use mysqli->unbuffered_query() to save yourself from a memory bloat.

down

shoresofnowhere at gmail dot com ¶

15 years ago

Beware of the fact that the ->def property NEVER gets filled with the correct default field value, so it's totally USELESS.

This happens NOT for a bug in php (so don't go filling in a bug report), but happens BY DESIGN, since the MySQL C API call doesn't fill in this value, unless you call the mysql_list_fields() function, which Php doesn't.

See here for reference.
http://dev.mysql.com/doc/refman/5.0/en/c-api-datatypes.html

Also, be aware that if you're using a query which contains subqueries, the primary key/autoincrement flags do NOT get passed along, even if the field you're looking at is the primary autoincrement key of the master table:

SELECT * from (SELECT id from areas) AS subareas

and you'll find primary key and autoinc flags off on id field, even if id was the primary autoinc key of areas table.

This also is by design, i think, since it's supposed that if we're using a subquery then the primary key/autoinc stuff might have no sense at all, since in the result set we can compose fileds from many different tables.

Hoping this is useful, bye!

down

anatoliy at ukhvanovy dot name ¶

9 years ago

You can find all available data types here:
https://php.net/manual/ru/mysqli.constants.php
(search "MYSQLI_TYPE_" in your browser)

down

-1

Anonymous ¶

4 years ago

JSON type is 245 if anyone is wondering.

down

-1

bl at example dot com ¶

14 years ago

note that
"SELECT <timestamp-field>, ..."
will return the field with type 7 (timestamp) but with content like "2010-07-14 14:35:08". the point being it is a string.

"SELECT <timestamp-field> + 0, ..."
returns a type 5 (double) but while a number, is not seconds since epoch, but a number in MySQL's "YYYYMMDDHHMMSS" format, in this example:
20100714143508

(PHP 5.2.12)

down

-1

deluxmozart at yahoo dot de ¶

16 years ago

Here are some Numbers of Datatypes. I searched for it but i didn't find a list, where the datatypes of the numbers are listed.

so first I can give this:

    3    -    Int
    10    -    Date
    246    -    Decimal
    252    -     text
    253    -    VarChar
    254    -    Boolean

down

-3

gcdreak at example dot com ¶

15 years ago

I wrote a simple class to get info about fields.
Try it!

<?php
            class MysqlFieldsInfo implements Iterator
            {
                
                private $result;
                private $position;
                private $row;
                
                
                function __construct($result){
                    $this->result = $result;
                    $this->position = 0;
                    $this->rewind();    // W $results wewnętrzny wskaźnik może być przesunięty więc powracamy do początku
                }
                
                public function current(){
                    return $this->row;
                }
                
                public function next(){
                    $this->position++;
                    $this->row = $this->result->fetch_field();    
                }
                
                public function valid(){
                    return (boolean) $this->row;
                }
                
                public function key(){
                    return $this->position;
                }
                
                public function rewind(){
                    $this->position = 0;
                    $this->result->field_seek(0);
                    $this->next();
                }
                
                //    This function show data in table
                public function export(){
                    
                    echo '<table id="db_table_info">';
                    echo '<tr>
                                                <th>Name</th>
                                                <th>Orgname</th>
                                                <th>Table</th>
                                                <th>Orgtable</th>
                                                <th>Def</th>
                                                 <th>Max_length</th>
                                                 <th>Length</th>
                                                 <th>Charsetnr</th>
                                                 <th>Flags</th>
                                                 <th>Type</th>
                                                  <th>Decimals</th>
                                          </tr>';
                    while($this->valid()){
                        echo '<tr>';
                        printf("\n\t<td>%s</td>\n", $this->current()->name);
                        printf("\t<td>%s</td>\n", $this->current()->orgname);
                        printf("\t<td>%s</td>\n", $this->current()->orgtable);
                        printf("\t<td>%s</td>\n", $this->current()->def);
                        printf("\t<td>%s</td>\n", $this->current()->max_length);
                        printf("\t<td>%s</td>\n", $this->current()->length);
                        printf("\t<td>%s</td>\n", $this->current()->charsetnr);
                        printf("\t<td>%s</td>\n", $this->current()->flags);
                        printf("\t<td>%s</td>\n", $this->current()->type);
                        printf("\t<td>%s</td>\n", $this->current()->decimals);

                        echo '</tr>';        
            
                        $this->next();
                    }
                    
                    echo '</table>';
                }
            }
?>

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