MySql JOINS And Count（）函数：#1054-未知列'；T.parent'；在'；关于第'条；

这是我的疑问：

SELECT A.term_id, 
       B.name, 
       counts
FROM wp_term_taxonomy A
LEFT JOIN (
SELECT COUNT( C.parent ) AS counts
FROM wp_term_taxonomy C
GROUP BY C.term_id
) AS T ON A.term_id = T.parent -- This line causes error
JOIN wp_terms B ON A.term_id = B.term_id
WHERE A.taxonomy =  'product_cat'
AND A.parent =0

我在运行此语法时遇到此错误：

#1054-on子句中的未知列“T.parent”

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如何正确引用带有ON的子查询select语句？

对于不存在的列，不能使用ON子句联接表（在您的情况下，不在自动生成的表t中进行选择）

您应该在t表中添加父列，例如：

SELECT A.term_id, B.name, counts
FROM wp_term_taxonomy A
LEFT JOIN (
  SELECT C.term_id as parent, COUNT( C.parent ) AS counts
  FROM wp_term_taxonomy C
  GROUP BY C.term_id
) AS T ON A.term_id = T.parent /* This line causes error*/
JOIN wp_terms B ON A.term_id = B.term_id
WHERE A.taxonomy =  'product_cat'
AND A.parent =0

---

对于不存在的列，不能使用on子句联接表（如果未在动态生成的表t中进行选择）

您应该在t表中添加父列，例如：

SELECT A.term_id, B.name, counts
FROM wp_term_taxonomy A
LEFT JOIN (
  SELECT C.term_id as parent, COUNT( C.parent ) AS counts
  FROM wp_term_taxonomy C
  GROUP BY C.term_id
) AS T ON A.term_id = T.parent /* This line causes error*/
JOIN wp_terms B ON A.term_id = B.term_id
WHERE A.taxonomy =  'product_cat'
AND A.parent =0