MySQL选择为special，输出排除空版本

这是我的sql语句，因为您可以看到select类别为special，我如何才能只获取special不为NULL

SELECT p.product_id, 

(SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND ps.customer_group_id = '1' 
    AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW()))   
    ORDER BY ps.priority 
    ASC, ps.price ASC LIMIT 1) AS special 

FROM oc_product_to_category p2c 
LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) 

WHERE AND p.status = '1' AND p.date_available <= NOW() 

AND p2c.category_id = '20' 

GROUP BY p.product_id ORDER BY p.sort_order ASC LIMIT 0,5

通过上述陈述，我有以下输出：

我尝试在可用的日期后添加WHERE，但没有结果。我尝试使用special不为NULL，它显示：“where子句”中的未知列“special”

在这件事上谁能帮忙？ 谢谢

special是一个别名，您正在将它分配给逻辑的输出，这发生在执行where子句之后，因此特殊列是未知的

试试这个：

Select * 
from
(
SELECT p.product_id, 

(SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND ps.customer_group_id = '1' 
    AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW()))   
    ORDER BY ps.priority 
    ASC, ps.price ASC LIMIT 1) AS special 

FROM oc_product_to_category p2c 
LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) 

WHERE AND p.status = '1' AND p.date_available <= NOW() 

AND p2c.category_id = '20' 

GROUP BY p.product_id ORDER BY p.sort_order ASC 
) mytemp where mytemp.special is not null

LIMIT 0,5

---

您需要在alias上设置筛选器，如下所示：-

SELECT user_name AS SPL FROM `apc_users` 
WHERE 1 
HAVING SPL IS NOT NULL 
ORDER BY `apc_users`.`user_name` ASC

就你而言：-

SELECT p.product_id, 

(SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND ps.customer_group_id = '1' 
    AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW()))   
    ORDER BY ps.priority 
    ASC, ps.price ASC LIMIT 1) AS special 

FROM oc_product_to_category p2c 
LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) 

WHERE AND p.status = '1' AND p.date_available <= NOW() 

AND p2c.category_id = '20' HAVING special IS NOT NULL

GROUP BY p.product_id ORDER BY p.sort_order ASC LIMIT 0,5

只需使用内部连接而不是左连接

---

试试看，这真的对你有用

SELECT p.product_id, 

(SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND price IS NOT NULL AND ps.customer_group_id = '1' 
    AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW()))   
    ORDER BY ps.priority 
    ASC, ps.price ASC LIMIT 1) AS special 

FROM oc_product_to_category p2c 
LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) 

WHERE AND p.status = '1' AND p.date_available <= NOW() 

AND p2c.category_id = '20' 

GROUP BY p.product_id ORDER BY p.sort_order ASC LIMIT 0,5

---

不确定，为什么人们投票否决你，我发现你的解决方案是最好的，并且解释得很好。谢谢其他也谢谢你的投入@Shiro:很好，它很有帮助。这个查询不会解决问题，事实上它有语法错误？？？看起来你从我的解决方案中复制了…@SashiKant我没有复制你的答案。内部联接必须用于此目的，因为它除了空值之外。现在，根据上帝的创造，我们是人类。。。正当因此，作为一个人，我们应该使用我们的大脑，我们必须记住，在成为程序员之前，我们是人。。因此，随着你知识的增长，请增加你的幽默感和湿度。。。。对，兄弟，永远不要低估任何人。。。如果我的评论伤害了你，那么我很抱歉。。。你可以给我负面的评价，我不在乎。。。但我只是说实话…奇怪的是，我们都想到了一个相同的别名。。。但我担心的是，您的查询无法运行，请重新检查

SELECT p.product_id, 

(SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND price IS NOT NULL AND ps.customer_group_id = '1' 
    AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW()))   
    ORDER BY ps.priority 
    ASC, ps.price ASC LIMIT 1) AS special 

FROM oc_product_to_category p2c 
LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) 

WHERE AND p.status = '1' AND p.date_available <= NOW() 

AND p2c.category_id = '20' 

GROUP BY p.product_id ORDER BY p.sort_order ASC LIMIT 0,5