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PHP中的mysql

Jun 06, 2016 pm 07:58 PM
mysql php query

对于mysql_query大家都很熟悉,下面先简单介绍下mysql_unbuffered_query mysql_unbuffered_query (PHP 4 = 4.0.6, PHP 5)mysql_unbuffered_query -- 向 MySQL 发送一条 SQL 查询,并不获取和缓存结果的行 说明resource mysql_unbuffered_query ( string quer

对于mysql_query大家都很熟悉,下面先简单介绍下mysql_unbuffered_query 

mysql_unbuffered_query 

(PHP 4 >= 4.0.6, PHP 5)mysql_unbuffered_query -- 向 MySQL 发送一条 SQL 查询,并不获取和缓存结果的行 

说明resource mysql_unbuffered_query ( string query [, resource link_identifier] ) 


mysql_unbuffered_query() 向 MySQL 发送一条 SQL 查询 query,但不像 mysql_query() 那样自动获取并缓存结果集。一方面,这在处理很大的结果集时会节省可观的内存。另一方面,可以在获取第一行后立即对结果集进行操作,而不用等到整个 SQL 语句都执行完毕。当使用多个数据库连接时,必须指定可选参数 link_identifier。 

注意: mysql_unbuffered_query() 的好处是有代价的:在 mysql_unbuffered_query() 返回的结果集之上不能使用 mysql_num_rows() 和 mysql_data_seek()。此外在向 MySQL 发送一条新的 SQL 查询之前,必须提取掉所有未缓存的 SQL 查询所产生的结果行。 

以上是mysql_unbuffered_query 在php手册中的解释,上网查了很多对手册中已有的解释的解释,很多人希望有个实例来更好地理解这个函数的应用,我按照给的解释,做了个实例,仅供参考: 

 

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<span>$link</span> = <span>mysql_connect</span>('localhost','root','pwd'<span>);

</span><span>mysql_select_db</span>('dbname'<span>);

</span><span>$sql</span> = "SELECT * FROM tablename"<span>;

 

</span><span>/*</span><span>

注意以下两个$result,如果用mysql_query(),那么mysql_data_seek()函数将起作用,因为查询结果缓存了,如果用

mysql_unbuffered_query()函数,那么mysql_data_seek()不起作用,正如它在手册中的解释,不缓存。

</span><span>*/</span>

 

<span>$result</span> = <span>mysql_unbuffered_query</span>(<span>$sql</span>,<span>$link</span><span>);

</span><span>//</span><span>$result = mysql_query($sql,$link);</span>

 

<span>while</span> (<span>$row</span> = <span>mysql_fetch_array</span>(<span>$result</span>,<span> MYSQL_NUM)) {

        </span><span>printf</span> ("ID: %s  Name: %s", <span>$row</span>[0], <span>$row</span>[1<span>]);

 

}

 

 

</span><span>mysql_data_seek</span>(<span>$result</span>,0<span>);

 

</span><span>while</span> (<span>$row</span> = <span>mysql_fetch_array</span>(<span>$result</span>,<span> MYSQL_NUM)) {

        </span><span>printf</span> ("ID: %s  Name: %s", <span>$row</span>[0], <span>$row</span>[1<span>]);

}

 

</span><span>mysql_free_result</span>(<span>$result</span>);"

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参考文章: http://www.lai18.com/content/317207.html

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