pg_meta_data()
(PHP 4 >= 4.3.0, PHP 5, PHP 7)
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。
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';
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) ?>
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); } ?>
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
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($dbconn,'drop table foo'); Throws an error: pg_exec(): Query failed: ERROR: table "foo" does not exist in ...
The built in function does not provide any support for selecting a schema. If you need schema support and do not want to alter your SEARCH_PATH, the following function can provide it: function meta_data($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; }