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

例子 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)
  }
}

警告

本函数是实验性的。本函数的行为,包括函数名称以及其它任何关于本函数的文档可能会在没有通知的情况下随 PHP 以后的发布而改变。使用本函数风险自担。

参见 pg_convert()


add a note add a note User Contributed Notes
rburghol at vt dot edu
24-Jun-2005 09:37
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 04:31
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