检查mysql_query是否返回任何内容

Question

$query = "SELECT * FROM `table`";
$results = mysql_query($query, $connection);

如果'table'没有行.最简单的检查方法是什么？

Answer 1

Jeremy Ruten上面的答案很好并且执行得很快; 另一方面,它只给你行数而没有别的(如果你想要结果数据,你必须再次查询数据库).我用的是什么:

// only ask for the columns that interest you (SELECT * can slow down the query)
$query = "SELECT some_column, some_other_column, yet_another_column FROM `table`";
$results = mysql_query($query, $connection);
$numResults = mysql_num_rows($results);
if ($numResults > 0) {
   // there are some results, retrieve them normally (e.g. with mysql_fetch_assoc())
} else {
   // no data from query, react accordingly
}

Answer 2

您可以使用mysql_num_rows($ results)来检查是否返回了0行,或者使用这个更快的替代方法:

$query = "SELECT COUNT(*) AS total FROM table";
$results = mysql_query($query, $connection);
$values = mysql_fetch_assoc($results);
$num_rows = $values['total'];

Answer 3

或者,您只需检查mysql_fetch_assoc的结果是否为false.

$query = "SELECT * FROM `table`";
$results = mysql_query($query, $connection);
$Row = mysql_fetch_assoc($results);
if ($Row == false)
{
  $Msg = 'Table is empty';
}