sql - SELECT SQL 语法 For Count in WHERE 子句

Question

我正在尝试构建正确的 sql 语句 (Oracle) 以获取大于给定值的每个 customer_id 的 device_id 计数。例如，我想知道具有 3 个以上 device_id 的 customer_id。一个 device_id 只能关联一个 customer_id，而一个 customer_id 可能有多个 device_id。

Table:
device_id
customer_id
....

Data (device_id, customer_id):
00001, CUST1
00002, CUST1
00003, CUST1
00004, CUST1
00005, CUST2
00006, CUST2

Answer 1

获取拥有 3 台以上设备的客户：

select customer_id, count(device_id)
from YourTable
Group by customer_id
having count(device_id) > 3

Answer 2

您将需要使用GROUP BYandHAVING子句

select customer_id, count(device_id)
from YourTable
group by customer_id
having count(device_id) > 3

Answer 3

你需要的是有子句：

select customer_id, count(*)
from t
group by customer_id
having count(*) > 3