pg_meta_data

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

pg_meta_data — 获得表的元数据

说明

pg_meta_data ( resource $connection , string $table_name ) : array

pg_metadata() 以数组形式返回 table_name 表的定义。

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。使用本函数风险自担。

参数

connection: PostgreSQL database connection resource.
table_name: The name of the table.

返回值

以数组 array 形式返回表的定义，如果出错则返回 false。

范例

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>';
  }
?>

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

pg_convert() - 将关联的数组值转换为适合 SQL 语句的格式。

User Contributed Notes

shaman_master at list dot ru 28-Apr-2019 11:03


If parameter $extended not false:

<?php

array (size=2)

  'name' => 

    array (size=11)

      'num' => int 1

      'type' => string 'varchar' (length=7)

      'len' => int -1

      'not null' => boolean false

      'has default' => boolean true

      'array dims' => int 0

      'is enum' => boolean false

      'is base' => boolean true

      'is composite' => boolean false

      'is pesudo' => boolean false

      'description' => string '' (length=0)

  'id' => 

    array (size=11)

      'num' => int 2

      'type' => string 'int4' (length=4)

      'len' => int 4

      'not null' => boolean true

      'has default' => boolean true

      'array dims' => int 0

      'is enum' => boolean false

      'is base' => boolean true

      'is composite' => boolean false

      'is pesudo' => boolean false

      'description' => string '' (length=0)

?>

Hayley Watson 17-Jul-2017 02:34


To specify a schema as well as a table name, use the "schemaname.tablename" form as usual for PostgreSQL and the other functions in this extension. Without the prefix, of course, the default schema search path is used.



<?php

  $meta = pg_meta_data($dbconn, 'foo.bar'); // table "bar" in schema "foo"

  if (is_array($meta)) {

      var_dump($meta);

  }

?>

jsnell at e-normous dot com 12-Nov-2007 03:24


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 08:32


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 06:37


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 01:31


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