Question

我正在尝试创建一个按描述对项目进行分组的查询，然后计算过去3个月的项目，每个月都有自己的列。最终，我正在努力实现以下目标：

    +-------------+------------+------------+--------------------+
    | Description | This Month | Last Month | The Previous Month |
    +-------------+------------+------------+--------------------+
    | Item_1      |          4 |          3 |                  5 |
    | Item_2      |          3 |          0 |                  2 |
    | Item_3      |          1 |          3 |                  5 |
    +-------------+------------+------------+--------------------+

Answer 1

SELECT
    "Description",
    SUM(
      CASE
        WHEN "Date" > NOW() THEN 0
        WHEN "Date" > NOW() - INTERVAL 1 MONTH THEN 1
        ELSE 0
      END CASE
    ) AS "This month",
    SUM(
      CASE
        WHEN "Date" > NOW() - INTERVAL 1 MONTH THEN 0
        WHEN "Date" > NOW() - INTERVAL 2 MONTH THEN 1
        ELSE 0
      END CASE
    ) AS "Last month",
    SUM(
      CASE
        WHEN "Date" > NOW() - INTERVAL 2 MONTH THEN 0
        WHEN "Date" > NOW() - INTERVAL 3 MONTH THEN 1
        ELSE 0
      END CASE
    ) AS "The previous month"
FROM Items
WHERE "Date" > NOW() - INTERVAL 3 MONTH
GROUP BY "Description"

如何计算每个项目的多个特定值？

1 个答案: