SQL Server 2022 新函数之DATETRUNC 日期截断详解

CREATE TABLE #Orders (
    OrderID     INT,
    CustomerID  INT,
    OrderDate   DATETIME2,
    Amount      DECIMAL(10, 2)
)
INSERT INTO #Orders VALUES
(1,  101, '2024-03-15 09:32:47.123', 1500.00),
(2,  102, '2024-03-15 14:05:22.456', 800.00),
(3,  101, '2024-03-20 11:18:33.789', 2300.00),
(4,  103, '2024-04-02 08:55:01.234', 620.00),
(5,  102, '2024-04-18 16:44:59.567', 1100.00),
(6,  101, '2024-05-07 10:22:15.890', 3200.00),
(7,  103, '2024-05-25 13:30:45.123', 950.00),
(8,  102, '2024-06-10 09:15:30.456', 1750.00)

SELECT 
    OrderID,
    OrderDate,
    DATETRUNC(day, OrderDate) AS 截断到日
FROM #Orders

-- 按月汇总销售额
SELECT 
    DATETRUNC(month, OrderDate) AS 月份,
    COUNT(*)                    AS 订单数,
    SUM(Amount)                 AS 总金额
FROM #Orders
GROUP BY DATETRUNC(month, OrderDate)
ORDER BY 月份

-- 以前的写法，需要组合多个函数
GROUP BY DATEADD(month, DATEDIFF(month, 0, OrderDate), 0)
-- 或者
GROUP BY YEAR(OrderDate), MONTH(OrderDate)

SELECT 
    DATETRUNC(quarter, OrderDate) AS 季度起始日,
    COUNT(*)                      AS 订单数,
    SUM(Amount)                   AS 总金额
FROM #Orders
GROUP BY DATETRUNC(quarter, OrderDate)
ORDER BY 季度起始日

SELECT 
    OrderID,
    OrderDate,
    DATETRUNC(week,     OrderDate) AS 本周起始_周日,
    DATETRUNC(iso_week, OrderDate) AS 本周起始_周一
FROM #Orders

SELECT 
    OrderID,
    OrderDate,
    DATETRUNC(hour, OrderDate)   AS 截断到小时,
    DATETRUNC(minute, OrderDate) AS 截断到分钟
FROM #Orders

SELECT 
    OrderID,
    OrderDate,
    DATEDIFF(day, DATETRUNC(month, OrderDate), OrderDate) AS 当月第几天
FROM #Orders