SQL技术求助：计算线上与POS销售占比拆分

需要从performancesales表中计算线上销售（ONLINE）与POS销售的占比拆分，已编写基础查询语句并得到部分结果，但不知道如何添加占比列——该列需按公式(POS/(POS+ONLINE))*100和(ONLINE/(POS+ONLINE))*100计算。

初始查询语句 #

SELECT
CASE
    WHEN saleschannel = 1 THEN 'ONLINE'
    WHEN saleschannel = 6 THEN 'ONLINE'
    WHEN saleschannel = 7 THEN 'ONLINE'
    WHEN saleschannel = 8 THEN 'ONLINE'
    ELSE 'POS'
END AS CHANNEL, 
COUNT(*) AS TICKET_QTY
FROM performancesales 
WHERE salesdate BETWEEN '2022-08-01' AND '2023-01-31'
AND saleschannel IN ('1','6', '7', '8', '14')
GROUP BY CHANNEL 
ORDER BY 2;

感谢Aaron提供的正确查询思路，已改写代码提升执行效率，最终代码如下：

优化后最终查询语句 #

SELECT
    channel,
    COUNT(*) AS ticket_qty,
    CAST(100.0 * COUNT(*) / SUM(COUNT(*)) OVER() AS DECIMAL(10,2)) AS percentage_split
FROM (
    SELECT 
        CASE 
            WHEN saleschannel IN ('2','5','7') THEN 'ONLINE'
            WHEN saleschannel IN ('0','1','4','6','8') THEN 'POS'
            ELSE 'OTHER - (AGGREGATOR)'
        END AS channel, 
        1 AS ticket
    FROM performancesales 
    WHERE 
        salesdate BETWEEN '2022-08-01' AND '2023-01-31' 
        AND saleschannel IN ('0','1','2','3','4','5','6','7','8')
) t
GROUP BY channel;

内容的提问来源于stack exchange，提问作者Henry Okwuenu