需要有关T-SQL查询的帮助

Question

我有一个与此类似的位置（地址）表：

location_id int identity (primary key)
contact_id int (foreign key to contact table; one-to-many relationship from contacts to locations)
<address info>
is_primary int (1 if this is the contact's primary address, zero otherwise)

每个联系人只能有一个主要地址。由于最近的数据上传出错，此规则已被违反，我现在有多个联系人拥有多个主要地址。我需要帮助制定查询以找出哪些查询。理想情况下，我希望输出为：

contact_id       count(is_primary)

我不知道该怎么做，非常感谢您的帮助。谢谢。

Answer 1

SELECT contact_id, SUM(IS_PRIMARY) 
FROM table_name 
GROUP BY contact_id 
HAVING SUM(IS_PRIMARY) > 1