SQL-几个日期函数

/*
    人员：LDH
    功能：SQL-几个日期函数
    日期：2018-7-20
 */

USE TSQLFundamentals2008;
GO

SELECT orderid,
    orderdate
FROM Sales.Orders;

SELECT TOP (8)
    orderid,
    orderdate
FROM Sales.Orders
WHERE orderdate > '20080301';

SELECT TOP (8)
    orderid,
    orderdate
FROM Sales.Orders
WHERE orderdate > CAST('20080301' AS DATETIME);

-- 年月日时分秒
SELECT DATEPART(YEAR, GETDATE()) AS '年',
    DATEPART(MONTH, GETDATE()) AS '月',
    DATEPART(DAY, GETDATE()) AS '日',
    DATEPART(HOUR, GETDATE()) AS '时',
    DATEPART(MINUTE, GETDATE()) AS '分',
    DATEPART(SECOND, GETDATE()) AS '秒';

-- 特殊的几个
SELECT DATEPART(DAYOFYEAR, GETDATE()) AS '从年初到现在的天数',
    DATEPART(WEEKDAY, GETDATE()) AS '一周的第几天',
    DATEPART(WEEK, GETDATE()) AS '今年的第几周';

SELECT GETDATE() AS 'CurrentDate',
    DATEADD(MONTH, 2, GETDATE()) AS 'FutureDate';

SELECT GETDATE() AS 'CurrentDate',
    DATEADD(YEAR, 2, GETDATE()) AS 'FutureDate';

-- 计算个人年龄
SELECT DATEDIFF(YEAR, '19890125', '20180720') AS '我的年龄';

-- 建国周年数
SELECT DATEDIFF(YEAR, CAST('19491001' AS DATETIME), GETDATE()) AS '建国周年数';