(PHP 4 >= 4.0.6, PHP 5)
mysql_unbuffered_query — Send an SQL query to MySQL without fetching and buffering the result rows
Questa enstensione deprecata da PHP 5.5.0, e sarà rimossa in futuro. Al suo posto, usare l'estensione MySQLi o PDO_MySQL. Vedere anche la guida MySQL: scelta dell'API e le FAQ relative per ulteriori informazioni. Le alternative a questa funzione includono:
mysql_unbuffered_query() sends the SQL query
query to MySQL without automatically
fetching and buffering the result rows as
mysql_query() does. This saves a considerable
amount of memory with SQL queries that produce large result sets,
and you can start working on the result set immediately after the
first row has been retrieved as you don't have to wait until the
complete SQL query has been performed. To use
mysql_unbuffered_query() while multiple database
connections are open, you must specify the optional parameter
link_identifier to identify which connection
you want to use.
queryThe SQL query to execute.
Data inside the query should be properly escaped.
link_identifierLa connessione MySQL. Se
l'identificativo di connessione non è specificato, l'ultima connessione aperta da
mysql_connect() viene assunta. Se questa connessione non è trovata, si
cercherà di crearne una come se mysql_connect() fosse stata chiamata
senza argomenti. Se una connessione non è trovata oppure non viene stabilita, un
avviso di livello E_WARNING viene generato.
For SELECT, SHOW, DESCRIBE or EXPLAIN statements,
mysql_unbuffered_query()
returns a resource on success, or false on
error.
For other type of SQL statements, UPDATE, DELETE, DROP, etc,
mysql_unbuffered_query() returns true on success
or false on error.
Nota:
The benefits of mysql_unbuffered_query() come at a cost: you cannot use mysql_num_rows() and mysql_data_seek() on a result set returned from mysql_unbuffered_query(), until all rows are fetched. You also have to fetch all result rows from an unbuffered SQL query before you can send a new SQL query to MySQL, using the same
link_identifier.
Don't let the two hands confuse you, these are both advantages (they should really be on the same hand):
On the one hand, this saves a considerable amount of memory with SQL queries that produce large result sets.
On the other hand, you can start working on the result set immediately ...You are NOT required to read all rows from the resultset when using unbuffered query, you may opt out at any time and use mysql_free_result. Imagine looking at 1 million row when the first 50 suffice? Just free the result and you are good to go again.If using optimized MyISAM tables I guess there is a big advantage with this function as it is possible to do selects and inserts on the same time as long as no rows in the table gets updated.