可以使用窗口函数ROW_NUMBER()来为每个组中的行添加序列号,并在添加时应用约束条件。以下是一个示例查询,它将“customers”表中每个“city”中的客户按照年龄排序,然后为每个“city”添加序列号,但仅为年龄小于50岁的客户添加序列号。
SELECT customer_id, customer_name, city, age,
ROW_NUMBER() OVER (PARTITION BY city ORDER BY age) as seq
FROM customers
WHERE age < 50
ORDER BY city, seq;
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