Question

晚上好！我如何COALESCE按COUNT(*)查询分组？

SELECT categories.name, COALESCE(COUNT(*), 0) as total FROM questions
  INNER JOIN categories
    ON questions.categoryid = categories.categoryid
GROUP BY name
ORDER BY total DESC;

我阅读了文档，这是执行此操作的主要解决方案，但它没有使用total = 0返回类别。

亲切的问候

Answer 1

count()的返回值无效，因此您不需要coalesce

你可能试着这个吗？

SELECT categories.name, COUNT(questions.categoryid) as total 
FROM questions
RIGHT OUTER JOIN categories
    ON questions.categoryid = categories.categoryid
GROUP BY name
ORDER BY total DESC;

合并计数等于0组

1 个答案: