sqlplus添加列标题

Question

我正在使用oracle中的sqlplus，并试图找出创建客户列表的方法，并根据以下条件对它们进行分类：

• 如果帐户#为1，则将其归类为“入门级”
• 如果帐户#为2-3，则将其归类为“增长”。
• 如果帐户#大于4，则将其归类为“成熟”

然后创建一个预期的输出(我已将其作为图像附加)。

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为此，我也附上了ERD。

这就是我到目前为止所拥有的。

SELECT DISTINCT first_name "First",
                surname "Last",
                customer_number "Cust #",
                account_type "# of Accts"
  FROM (  SELECT first_name,
                 surname,
                 customer_number,
                 account_type
            FROM wgb_customer
                 JOIN wgb_account USING (customer_number)
                 JOIN wgb_account_type USING (account_type)
        ORDER BY account_type);

请帮帮忙！这是预期的输出！

First       Last        Cust#         # of Accts     Level
----------------------------------------------------------------        
Peter      Chen         2566217             3         Growing           
Byron      Griffith     1113004             1         Entry Level
Patricia   Lee          9871332             1         Entry Level
Henri      Poincare     1113501             3         Growing   
John       Synge        1112401             2         Growing   

Answer 1

这听起来像是使用case表达式进行聚合：

select c.first_name, c.surname, c.customer_number,
       count(*) as num_accounts,
       (case when count(*) = 1 then 'Entry Level'
             when count(*) <= 3 then 'Growing'
             else 'Mature'
        end) as level
from wgb_customer c join
     wgb_account a
     using (customer_number) 
group by c.first_name, c.surname, c.customer_number;