PDO :: fetchAll与PDO :: fetch在循环中

几乎没有200k随机记录的基准。与预期的一样，fetchAll方法更快，但需要更多的内存。

Result : fetchAll : 0.35965991020203s, 100249408b fetch : 0.39197015762329s, 440b 使用的基准代码：

setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $sql = 'SELECT * FROM test_table WHERE 1'; $stmt = $dbh->query($sql); $data = array(); $start_all = microtime(true); $data = $stmt->fetchAll(); $end_all = microtime(true); $stmt = $dbh->query($sql); $data = array(); $start_one = microtime(true); while($data = $stmt->fetch()){} $end_one = microtime(true); // Second benchmark : memory usage $stmt = $dbh->query($sql); $data = array(); $memory_start_all = memory_get_usage(); $data = $stmt->fetchAll(); $memory_end_all = memory_get_usage(); $stmt = $dbh->query($sql); $data = array(); $memory_end_one = 0; $memory_start_one = memory_get_usage(); while($data = $stmt->fetch()){ $memory_end_one = max($memory_end_one, memory_get_usage()); } echo 'Result :
fetchAll : ' . ($end_all - $start_all) . 's, ' . ($memory_end_all - $memory_start_all) . 'b
fetch : ' . ($end_one - $start_one) . 's, ' . ($memory_end_one - $memory_start_one) . 'b
'; 分享来源：stack overflow