Mysql 在一个查询中使用两个COUNT语句时出现未知列错误

我试图在一个SQL查询中运行两次不同的计数，但出现以下错误：

未找到列：“on子句”中的1054未知列“po.product_id”

以下是sql：

SELECT COUNT(*) vouchersleft, `prod_name`,
        `start_date`, 
        `end_date`,
        `reg_price`,
        `sale_price`,
        bbp.`prod_id`,
        `vouch_limits`,
        `sp_name`,
        `order_id`,
        `img_name`,
        `outlets`
        FROM `vouchers` as `v`
        INNER JOIN `bb_products` as `bbp` ON bbp.`prod_id` = v.`product_id`
        INNER JOIN `service_providers` as `sp` ON sp.`service_provider_id` = bbp.`provider_id`
        INNER JOIN `prod_pics` as `pp` ON pp.`prod_id` = bbp.`prod_id`
        INNER JOIN (SELECT COUNT(DISTINCT `outlet_id`) AS `outlets` FROM `prod_outlets` GROUP BY `product_id`) as `po` ON po.`product_id` = bbp.`prod_id`
        WHERE `frontend` = :frontend
        AND bbp.`featured` = :featured
        AND `order_id` = :order_id
        AND pp.`featured` = :featured_img
        GROUP BY bbp.`prod_id`

---

将列包括在

分组依据中是不够的。您还需要将其包括在
选择中：

SELECT product_id, COUNT(DISTINCT `outlet_id`) AS `outlets`
FROM `prod_outlets`
GROUP BY `product_id`

将列包括在
分组依据中是不够的。您还需要将其包括在
选择中：

SELECT product_id, COUNT(DISTINCT `outlet_id`) AS `outlets`
FROM `prod_outlets`
GROUP BY `product_id`

如果要按列联接，则必须通过
SELECT
语句返回。在您选择的列列表中包括
product\u id

更改：

INNER JOIN (SELECT COUNT(DISTINCT `outlet_id`) AS `outlets` FROM `prod_outlets` GROUP BY `product_id`) as `po` ON po.`product_id` = bbp.`prod_id`

致：

如果未选择列，
product\u id
在此中间表（此处命名为
po
）之外不可见。这就是为什么会出现一个错误未知列，因为只有已知列是
outlets
，如果要通过该列加入，则必须通过
SELECT
语句返回该列。在您选择的列列表中包括
product\u id

更改：

INNER JOIN (SELECT COUNT(DISTINCT `outlet_id`) AS `outlets` FROM `prod_outlets` GROUP BY `product_id`) as `po` ON po.`product_id` = bbp.`prod_id`

致：

如果未选择列，
product\u id
在此中间表（此处命名为
po
）之外不可见。这就是为什么会出现错误未知列，因为唯一已知列是
outlets
为什么不直接加入

SELECT COUNT(*) vouchersleft, `prod_name`,
        `start_date`, 
        `end_date`,
        `reg_price`,
        `sale_price`,
        bbp.`prod_id`,
        `vouch_limits`,
        `sp_name`,
        `order_id`,
        `img_name`,
         COUNT(DISTINCT po.`outlet_id`) AS `outlets`
        FROM `vouchers` as `v`
        INNER JOIN `bb_products` as `bbp` ON bbp.`prod_id` = v.`product_id`
        INNER JOIN `service_providers` as `sp` ON sp.`service_provider_id` = bbp.`provider_id`
        INNER JOIN `prod_pics` as `pp` ON pp.`prod_id` = bbp.`prod_id`
        RIGHT JOIN `prod_outlets`  as `po` ON po.`product_id` = bbp.`prod_id`
        WHERE `frontend` = :frontend
        AND bbp.`featured` = :featured
        AND `order_id` = :order_id
        AND pp.`featured` = :featured_img
        GROUP BY bbp.`prod_id`

为什么不直接加入

SELECT COUNT(*) vouchersleft, `prod_name`,
        `start_date`, 
        `end_date`,
        `reg_price`,
        `sale_price`,
        bbp.`prod_id`,
        `vouch_limits`,
        `sp_name`,
        `order_id`,
        `img_name`,
         COUNT(DISTINCT po.`outlet_id`) AS `outlets`
        FROM `vouchers` as `v`
        INNER JOIN `bb_products` as `bbp` ON bbp.`prod_id` = v.`product_id`
        INNER JOIN `service_providers` as `sp` ON sp.`service_provider_id` = bbp.`provider_id`
        INNER JOIN `prod_pics` as `pp` ON pp.`prod_id` = bbp.`prod_id`
        RIGHT JOIN `prod_outlets`  as `po` ON po.`product_id` = bbp.`prod_id`
        WHERE `frontend` = :frontend
        AND bbp.`featured` = :featured
        AND `order_id` = :order_id
        AND pp.`featured` = :featured_img
        GROUP BY bbp.`prod_id`

您通常按所选的所有列进行分组，设置函数参数的列除外。您通常按所选的所有列进行分组，设置函数参数的列除外。