[英]MySQL select only unique values
我有两张桌子。
客户:
+--------------+-------------+
| CLIENT_ID | LABEL |
+--------------+-------------+
| 123 | label1 |
+--------------+-------------+
| 123 | label3 |
+--------------+-------------+
| 456 | label1 |
+--------------+-------------+
| 789 | label2 |
+--------------+-------------+
| 987 | label2 |
+--------------+-------------+
| 987 | label4 |
+--------------+-------------+
经理:
+----+--------------+
| ID | CLIENT_ID |
+----+--------------+
| 1 | 123 |
+----+--------------+
| 1 | 456 |
+----+--------------+
| 2 | 456 |
+----+--------------+
| 3 | 789 |
+----+--------------+
| 3 | 987 |
+----+--------------+
| 4 | 789 |
+----+--------------+
我需要来自经理的 select ID,这些经理只有带有标签“label1”或“label2”的客户,而没有带有其他标签的客户。 生成的 output 应该类似于 2 和 4。
我试着做
select m.id
from managers m
join clients c on m.client_id = c.client_id
where c.label in ('label1', 'label2');
但它返回所有ID。
关。 只需添加聚合:
select m.id
from managers s join
clients c
on m.client_id = c.client_id
where c.label in ('label1', 'label2')
group by m.id
having count(distinct c.label) = 2;
如果您只想要具有这两个标签的客户端,请使用:
select m.id
from managers s join
clients c
on m.client_id = c.client_id
group by m.id
having count(distinct c.label) = 2;
select m.id
from managers s join
clients c
on m.client_id = c.client_id
group by m.id
having count(distinct case when c.label in ('label1', 'label2') then c.label end) = 2 and
count(distinct c.label) = 2;
或者,更有效地:
having sum(c.label = 'label1') > 0 and
sum(c.label = 'label2') > 0 and
sum(c.label not in ('label1', 'label2')) = 0;
使用group by
如下:
select m.id
from managers m
join clients c on m.client_id = c.client_id
where c.label in ('label1', 'label2')
group by m.id
having count(*) = 1;
请尝试group by
并having
此处声明以获取唯一记录
SELECT ID FROM `Clients` c
left join Managers m on (c.client_id = m.CLIENT_ID)
where LABEL in ('label1', 'label2')
group by ID having count(*) = 1
谢谢
您可以使用 CTE 获取与特定经理关联的客户标签有效的出现次数:
with r as (select m.id id, sum(c.label in ('label1', 'label2')) c1, count(*) c2
from managers m join clients c on m.client_id = c.client_id group by m.id)
select id from r where c1 = c2;
Output:
ID |
---|
2 |
4 |
加入表,按经理分组并在HAVING
子句中为您的条件使用条件聚合:
SELECT m.id
FROM managers m INNER JOIN clients c
ON m.client_id = c.client_id
GROUP BY m.id
HAVING MAX(c.label IN ('label1', 'label2')) = 1
AND MAX(c.label NOT IN ('label1', 'label2')) = 0
如果客户端同时具有标签'label1'
和'label2'
并且可以扩展到更多标签,这也将起作用。
请参阅演示。
结果:
ID |
---|
2 |
4 |
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