mysql - SQL : Creating new columns using Case When, 分组 ID

Question

如何使用 CASE WHEN、GROUPING_ID() 和 ROLLUP() 语法在 SQL 中创建全新列？

到目前为止我已经尝试过:

SELECT Country, ContactTitle, COUNT(ContactTitle) AS Count
,CASE(
WHEN
GROUPING_ID(Legend) = 0 THEN ' '
WHEN
GROUPING_ID(Legend) = 1 THEN 'SUBTOTAL(Country)')
GROUP BY ROLLUP(Country, ContactTitle)
FROM dbo.Customers

Answer 1

SELECT Country, ContactTitle, COUNT(ContactTitle) AS Count, 
CASE 
    WHEN GROUPING_ID(Country,ContactTitle) = 0 THEN ''
    WHEN GROUPING_ID(Country,ContactTitle) = 1 THEN CONCAT('Subtotal for ',Country)
END AS Legend
FROM dbo.Customers
GROUP BY ROLLUP(Country, ContactTitle);