使用 oracle 的一个案例语句中的多个条件

Question

我有以下 sql 和结果：

SELECT oh.order_id,disallow_short_ship,sm.number
FROM table1 oh
    LEFT JOIN table2 sm
        ON sm.client_id = oh.client_id
            AND sm.site_id = oh.from_site_id
            AND sm.order_id = oh.order_id
WHERE oh.order_id = 'abc'
GROUP BY oh.order_id,oh.disallow_short_ship,sm.number
ORDER BY oh.order_id desc;

结果：

order_id   disallow_short_ship      number 
abc        null                     2107
abc        null                     2108

预期的结果是把case条件 如果订单的结果不止一个，那么 比较两个数字列， 更大的数字（2108）应该有disallow_short_ship = 'Y' 结果是少数 (2107) disallow_short_ship = 'N'。

我尝试为disallow_short_ship 列写case 语句，但我需要设置两个条件吗 在一个案例陈述中。

预期结果：

order_id   disallow_short_ship   number 
abc        N                     2107
abc        Y                     2108

Answer 1

使用窗口函数和case 表达式：

SELECT oh.order_id, disallow_short_ship, sm.number,
       (CASE WHEN COUNT(*) OVER (PARTITION BY oh.order_id) > 1 AND
                  ROW_NUMBER() OVER (PARTITION BY oh.order_id ORDER BY number) = 1
             THEN 'N'
             WHEN COUNT(*) OVER (PARTITION BY oh.order_id) > 1 AND
                  ROW_NUMBER() OVER (PARTITION BY oh.order_id ORDER BY number DESC) = 1
             THEN 'Y'
             ELSE disallow_short_ship
        END) as disallow_short_ship             
FROM table1 oh LEFT JOIN
     table2 sm
     ON sm.client_id = oh.client_id AND
        sm.site_id = oh.from_site_id AND
        sm.order_id = oh.order_id
WHERE oh.order_id = 'abc'
GROUP BY oh.order_id, oh.disallow_short_ship, sm.number
ORDER BY oh.order_id desc;