在另一个mysql命令中使用一个mysql命令的结果?

如果我理解你想要完成的事情,你会发现所有的事情都是在一个特定的事件后一天开始的。对的?在这种情况下,您要做的是一个自连接,即将一个表连接到它自己。您需要为表中的至少一个实例提供别名,以便SQL能够区分它们。

所以可能是这样:

SELECT e2.id
FROM mm_eventlist_dates e1
join mm_eventlist_dates e2 on e2.startdate = date_add(e1.enddate, INTERVAL 1 DAY)
where e1.id=$id

是否有原因不能将它们组合到一个查询中?

SELECT m1.id FROM mm_eventlist_dates m1  
JOIN mm_eventlist_dates m2 ON m1.startdate = date_add(m2.enddate, INTERVAL 1 DAY)  
WHERE m2.id = $id

mysql_query()返回结果集,而不是实际的数据库项。要执行上述操作,请执行类似的操作(不包括错误检查等):

//select the event end date of event ID
$sql = "SELECT enddate FROM mm_eventlist_dates WHERE id = $id";
$result = mysql_query($sql);

$enddateRow = mysql_fetch_array($result);

//plug in the event end date, find event that starts the next day
$sql = "SELECT id FROM mm_eventlist_dates WHERE startdate = date_add('" . $enddateRow["enddate"] . "', INTERVAL 1 DAY)";
$result = mysql_query($sql);
$row = mysql_fetch_array($result);
echo "Next Event ID" . $row['id'];

您不能在日期添加中直接使用$result。调用mysql_fetch_array(稍后再做几行),并使用$row['enddate']。

//select the event end date of event ID
$sql = "SELECT enddate FROM mm_eventlist_dates WHERE id = $id";
$result = mysql_query($sql);
$row = mysql_fetch_array($result);
$enddate = $row['enddate'];

//plug in the event end date, find event that starts the next day
$sql = "SELECT id FROM mm_eventlist_dates WHERE startdate = date_add($enddate, INTERVAL 1 DAY)";
$result = mysql_query($sql);
$row = mysql_fetch_array($result);
echo "Next Event ID" . $row['id'];

我想

不能在另一个查询中直接使用mysql_查询的结果,需要先获取值。

而不是

$result = mysql_query($sql);

//plug in the event end date, find event that starts the next day
$sql = "SELECT id FROM mm_eventlist_dates WHERE startdate = date_add($result, INTERVAL 1 DAY)";

尝试

   $result = mysql_query($sql);
   $enddate = mysql_fetch_assoc($result);

    //plug in the event end date, find event that starts the next day
    $sql = "SELECT id FROM mm_eventlist_dates WHERE startdate = date_add($enddate, INTERVAL 1 DAY)";

试试这个

//select the event end date of event ID
$sql = "SELECT enddate FROM mm_eventlist_dates WHERE id = $id";
$result = mysql_query($sql);

$row = mysql_fetch_assoc($result)
//plug in the event end date, find event that starts the next day
$sql = "SELECT id FROM mm_eventlist_dates WHERE startdate = date_add(".$row['enddate'].", INTERVAL 1 DAY)";
$result = mysql_query($sql);
$row = mysql_fetch_array($result);
echo "Next Event ID" . $row['id'];