php - 给出警告 : mysql_fetch_assoc() expects parameter 1 to be resource, bool 值

Question

我在尝试执行以下查询时收到此错误:

$sql = mysql_query("select c.id as id_car, c.year, c.make, c.model, c.type, c.colour, 
                           (select count(*) from `parts` where `id_car`=c.id and `is_packaged`='yes') as partcount
                           from `cars` as c 
                           where partcount > 0
                           group by c.id
                           order by `id` desc");

问题似乎出在 partcount > 0。在尝试进行比较时，似乎将 0 视为 bool 值？

Answer 1

$sql 的值可能为 false。如果您尝试执行的查询未能执行(通常是由于 SQL 中的语法错误)，就会发生这种情况。

通常，您希望查询代码如下所示:

if ($result = mysql_query ('SELECT * FROM foo WHERE bar = \'baz\''))
{
    // resultset processing goes here
    while ($row = mysql_fetch_assoc ($result))
    {
    }
}
else
{
    echo (mysql_error ());
}