Question

在尝试在查询中执行2次计数时发现此错误

首先向您展示查询：

$sql = mysql_query("select c.id, c.number, d.name, 
                    (select count(*) from `parts` where `id_container`=c.id group by `id_car`) as packcount,
                    (select count(*) from `parts` where `id_container`=c.id) as partcount
                    from `containers` as c
                    left join `destinations` as d on (d.id = c.id_destination)
                    order by c.number asc") or die(mysql_error());

现在parts表有两个我需要在计数中使用的字段： id_car id_container

id_car =该部件所用汽车的ID id_container =零件所在容器的ID

packcount我想要的是每个集装箱的总车数对于partcount，我想要它计算每个容器的总份数

Answer 1

这是因为GROUP BY你正在使用

尝试类似

的内容

(select count(distinct id_car) from `parts` where `id_container`=c.id)

在你的子查询中（现在无法检查）

修改

PFY - 我认为UNIQUE适用于索引

Answer 2

您在第一个子查询中的分组导致返回多行，您可能需要运行单独的查询才能获得您要查找的结果。

Answer 3

此子查询可能会返回多行。

(select count(*) from `parts` where `id_container`=c.id group by `id_car`) as packcount, ...

所以，我建议尝试以下方法：

(select count(DISTINCT `id_car`) from `parts` where `id_container`=c.id) as packcount, ...

请参阅：COUNT(DISTINCT) on dev.mysql.com

和：QA on stackoverflow

子查询返回多行

3 个答案: