如何通过查询查找MySQL组中的唯一值？

MySQL表：数字

在此表中，ID是主键。NUM是随机值，CREATED是日期

我的问题是：

我的查询结果：

但我的预期结果是：

2018-03月的UniqueNum结果应为0。因为NUM 11在2018-01月已经存在。而且 2018-05月的UniqueNum结果应为0。因为2018-02月已经存在NUM 22

---

我想找到每个月的唯一号码。如何通过更新MySQL查询获得预期结果？请提供帮助。

您只需将表本身连接起来，然后只返回以前创建日期不存在的数字即可

SELECT
  DATE_FORMAT(n.CREATED,'%Y-%m') AS Month,
  COUNT(n.NUM) AS TotalNum,
  COUNT(un.NUM) AS UniqueNum
FROM
  `numbers` n
LEFT JOIN (SELECT ID, NUM FROM numbers n1 WHERE NOT EXISTS (SELECT 1 FROM numbers n2 WHERE n1.NUM = n2.NUM AND n2.CREATED < n1.CREATED)) un ON n.ID = un.ID 
GROUP BY
  DATE_FORMAT(n.CREATED,'%Y-%m')

现场观看它的工作

---

通常对我有效的解决方案是嵌套查询 希望这有帮助

SELECT
    Month,
    SUM(NUMCNT) AS TotalNum,
    COUNT(NUM) AS UniqueNum
FROM
    (
SELECT
    DATE_FORMAT(CREATED,'%Y-%m') AS Month,
    NUM,
    COUNT(NUM) AS NUMcnt
FROM
    `numbers`
GROUP BY
    Month,
    NUM
) a
;

---

非常感谢您的回答。当行数超过5K时，此查询花费的时间太长。有没有其他方法可以加快查询速度？请在另一个问题中提出这个问题。包括以下查询的结果：显示创建表编号\G，解释，从数字中显示索引；现在，通过向NUM字段添加索引，问题得到了解决。谢谢你

+---------+----------+-----------+
| Month   | TotalNum | UniqueNum |
+---------+----------+-----------+
| 2018-01 |    1     |     1     |
+---------+----------+-----------+
| 2018-02 |    1     |     1     |
+---------+----------+-----------+
| 2018-03 |    1     |     1     |
+---------+----------+-----------+
| 2018-04 |    2     |     1     |
+---------+----------+-----------+
| 2018-05 |    1     |     1     |
+---------+----------+-----------+

+---------+----------+-----------+
| Month   | TotalNum | UniqueNum |
+---------+----------+-----------+
| 2018-01 |    1     |     1     |
+---------+----------+-----------+
| 2018-02 |    1     |     1     |
+---------+----------+-----------+
| 2018-03 |    1     |     0     |
+---------+----------+-----------+
| 2018-04 |    2     |     1     |
+---------+----------+-----------+
| 2018-05 |    1     |     0     |
+---------+----------+-----------+

SELECT
  DATE_FORMAT(n.CREATED,'%Y-%m') AS Month,
  COUNT(n.NUM) AS TotalNum,
  COUNT(un.NUM) AS UniqueNum
FROM
  `numbers` n
LEFT JOIN (SELECT ID, NUM FROM numbers n1 WHERE NOT EXISTS (SELECT 1 FROM numbers n2 WHERE n1.NUM = n2.NUM AND n2.CREATED < n1.CREATED)) un ON n.ID = un.ID 
GROUP BY
  DATE_FORMAT(n.CREATED,'%Y-%m')

SELECT
    Month,
    SUM(NUMCNT) AS TotalNum,
    COUNT(NUM) AS UniqueNum
FROM
    (
SELECT
    DATE_FORMAT(CREATED,'%Y-%m') AS Month,
    NUM,
    COUNT(NUM) AS NUMcnt
FROM
    `numbers`
GROUP BY
    Month,
    NUM
) a
;