Question

第一张表：问题

+----+-----------+----------+------------+-------------+----------+-----------+-----------+-------+
| id | createdBy | question | attachment | contributor | doctorId | ipAddress | userAgent | views |
+----+-----------+----------+------------+-------------+----------+-----------+-----------+-------+
|  1 |         1 | hiii     | NULL       | NULL        |        3 | NULL      | NULL      |  NULL |
+----+-----------+----------+------------+-------------+----------+-----------+-----------+-------+

第二张表：视图

+----+-----------+--------+-------+------------+
| id | ipAddress | userId | count | questionId |
+----+-----------+--------+-------+------------+
|  1 | NULL      |      1 |  NULL |          1 |
+----+-----------+--------+-------+------------+

我想要数据问题表id，createdBy，question，count（从view表中查看问题的用户数= = 1）; 如何编写单个查询;

Answer 1

一个简单的COUNT（DISTINCT ......）应该这样做： -

SELECT COUNT(DISTINCT userId)
FROM view
WHERE question = 1

要获得有关问题的其他详细信息，请执行连接并添加GROUP BY子句

SELECT question.id,
        question.createdBy,
        question.question,
        COUNT(DISTINCT userId)
FROM view
INNER JOIN question
WHERE view.question = 1
GROUP BY id,
        createdBy,
        question

Answer 2

如果表名是问题而你的问题也是一个包含问题编号（id）的字段，而views字段包含问题的观看次数，那么你可以得到这样的观点。

select views from question where question=1;

是否可以编写单个查询？

2 个答案: