PostgreSQL 函数
在线手册：中文 英文
PHP手册

pg_meta_data

(PHP 4 >= 4.3.0, PHP 5)

pg_meta_data — 获得表的元数据

说明

array pg_meta_data ( resource $connection , string $table_name )

pg_metadata() 以数组形式返回 table_name 表的定义。如果出错则返回 FALSE。

Example #1 取得表的元数据

<?php
    $dbconn = pg_connect("dbname=publisher") or die("Could not connect");
    $meta = pg_meta_data($dbconn,'authors');
    if (is_array ($meta)) {
        echo '<pre>';
        var_dump ($meta);
        echo '</pre>';
    }
?>

上例输出如下： 

array(3) {
  ["author"]=>
  array(5) {
    ["num"]=>
    int(1)
    ["type"]=>
    string(7) "varchar"
    ["len"]=>
    int(-1)
    ["not null"]=>
    bool(false)
    ["has default"]=>
    bool(false)
  }
  ["year"]=>
  array(5) {
    ["num"]=>
    int(2)
    ["type"]=>
    string(4) "int2"
    ["len"]=>
    int(2)
    ["not null"]=>
    bool(false)
    ["has default"]=>
    bool(false)
  }
  ["title"]=>
  array(5) {
    ["num"]=>
    int(3)
    ["type"]=>
    string(7) "varchar"
    ["len"]=>
    int(-1)
    ["not null"]=>
    bool(false)
    ["has default"]=>
    bool(false)
  }
}

Warning

此函数是实验性的。 此函数的表象，包括名称及其相关文档都可能在未来的 PHP 发布版本中未通知就被修改。使用本扩展风险自担 。

参见 pg_convert()。

参数

connection

PostgreSQL database connection resource.

table_name

The name of the table.

返回值

An array of the table definition, or FALSE on error.

范例

Example #2 Getting table metadata

<?php
  $dbconn = pg_connect("dbname=publisher") or die("Could not connect");

  $meta = pg_meta_data($dbconn, 'authors');
  if (is_array($meta)) {
      echo '<pre>';
      var_dump($meta);
      echo '</pre>';
  }
?>

以上例程会输出：

array(3) {
["author"]=>
array(5) {
  ["num"]=>
  int(1)
  ["type"]=>
  string(7) "varchar"
  ["len"]=>
  int(-1)
  ["not null"]=>
  bool(false)
  ["has default"]=>
  bool(false)
}
["year"]=>
array(5) {
  ["num"]=>
  int(2)
  ["type"]=>
  string(4) "int2"
  ["len"]=>
  int(2)
  ["not null"]=>
  bool(false)
  ["has default"]=>
  bool(false)
}
["title"]=>
array(5) {
  ["num"]=>
  int(3)
  ["type"]=>
  string(7) "varchar"
  ["len"]=>
  int(-1)
  ["not null"]=>
  bool(false)
  ["has default"]=>
  bool(false)
}
}

参见

PostgreSQL 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 获得表的元数据

用户评论:

jsnell at e-normous dot com (12-Nov-2007 11:24)

The built in function does not provide any support for selecting a schema.  If you need schema support and do not want to alter your SEARCH_PATH, the following function can provide it:

 function meta_data($table, $schema = 'public')
    {
$result = pg_query_params("SELECT a.attname, a.attnum, t.typname, a.attlen, a.attnotNULL, a.atthasdef, a.attndims
FROM pg_class as c, pg_attribute a, pg_type t, pg_namespace n
WHERE a.attnum > 0
AND a.attrelid = c.oid
AND c.relname = $1
AND a.atttypid = t.oid
AND n.oid = c.relnamespace
AND n.nspname = $2
ORDER BY a.attnum", array($table, $schema));
$fields = array();
while($row = pg_fetch_array()) {
$fields['attname'] = $row;
}
        return $fields;
    }

yarnofmoo at gmail dot com (27-Jun-2007 04:32)

You can get some possibly more useful information with the query:

SELECT table_name, column_name, data_type, character_maximum_length FROM information_schema.columns WHERE table_name='tablename';

rburghol at vt dot edu (24-Jun-2005 02:37)

When querying on meta data from a temp table, the meta data seems to persist even if a fresh connection is established, where the temp table no longer exists.

 For example, if you create a connection and a temp table like so:
$dbconn1 = pg_connect('blah blah', , PGSQL_CONNECT_FORCE_NEW);
pg_exec($dbconn1,'create temp table foo as select 'foo' as namecol, 'bar' as valcol');

Then create a new connection

$dbconn2 = pg_connect('blah blah', , PGSQL_CONNECT_FORCE_NEW);

And query the meta data for table 'foo' in this new connection, it will report the facts about this table:
pg_meta_data($dbconn2,'foo');

"'Array ( [foo] => Array ( [num] => 1 [type] => varchar... "

However, trying to remove this table:
pg_exec($dbconn,'drop table foo');

Throws an error:
pg_exec(): Query failed: ERROR: table "foo" does not exist in ...

dmiller at NOSPAM dot judcom dot nsw dot gov dot au (18-Jun-2003 09:31)

This function seems to be case-sensitive on tablename (php-4.3.1)

The Array returned is of the following structure
['field name'] => Array
   (
     ['num'] => Field number starting at 1
     ['type'] => data type, eg varchar, int4
     ['len'] => internal storage size of field. -1 for varying
     ['not null'] => boolean
     ['has default'] => boolean
   )
     ......

for Varied size datatypes (varchar, text, etc)
you can get the max data length from the system table pg_attribute.atttypmod -4
eg.
select attnum, attname , atttypmod -4 as field_len
from pg_attribute, pg_class
where relname='$tablename'
and attrelid=relfilenode
and attnum>=1