SQL实现Excel COUNTIFS功能

Question

能否在SQL内实现类似Excel Countifs函数功能
例如 商家甲的A产品售卖200件，在表格中重复出现，则在统计列显示为2

Answer 1

连接查询+分组。

SELECT
    a.*,
    b.countif 
FROM
    `product` AS a
    JOIN ( SELECT NAME, merchant, count(*) AS countif FROM product GROUP BY NAME, merchant ) AS b ON b.NAME = a.NAME 
    AND b.merchant = a.merchant;