GROUP BY 和 DISTINCT 之间的区别

GROUP BY 与聚合函数结合使用。请考虑下表：

下面的查询使用 GROUP BY 执行聚合计算。

SELECT
    storeName,
    COUNT(*) AS total_nr_orders,
    COUNT(DISTINCT userId) AS nr_unique_customers,
    AVG(orderValue) AS average_order_value,
    MIN(orderDate) AS first_order,
    MAX(orderDate) AS lastOrder
FROM
    orders
GROUP BY
    storeName;

并将返回以下信息

虽然 DISTINCT 用于列出指定列的不同值的唯一组合。

SELECT DISTINCT
    storeName,
    userId
FROM
    orders;