日期处理
SQL Server 中的函数与存储过程编写
Meghan Kwartler
IT Consultant
GETDATE
SELECT GETDATE()
+-------------------------+
| 2019-02-27 13:11:59.590 |
+-------------------------+
DECLARE @CurrentDateTime AS datetime
SET @CurrentDateTime = GETDATE()
SELECT @CurrentDateTime
+-------------------------+
| 2019-02-27 13:14:36.517 |
+-------------------------+
-- DATEADD 语法：
DATEADD (datepart, number, date)
-- 根据 data_type 返回表达式
-- 2019/2/27 的后一天
SELECT DATEADD(day, 1, '2/27/2019')
+-------------------------+
| 2019-02-28 00:00:00.000 |
+-------------------------+
DATEADD 与 GETDATE
-- 昨天
SELECT DATEADD(d, -1, GETDATE())
+-------------------------+
| 2019-02-26 09:20:50.013 |
+-------------------------+
-- 昨日出租车乘客数
SELECT SUM(PassengerCount)
FROM YellowTripData
WHERE CAST(PickupDate as date) = DATEADD(d, -1, GETDATE())
还记得 DATEDIFF 吗？
SELECT DATEDIFF(day, '2/27/2019', '2/28/2019')
+---+
| 1 |
+---+
SELECT DATEDIFF(year, '12/31/2017', '1/1/2019')
+---+
| 2 |
+---+
-- 本周第一天
SELECT DATEADD(week, DATEDIFF(week, 0, GETDATE()), 0)
-- 第一步
GETDATE()
+-------------------------+
| 2019-02-27 10:33:39.713 |
+-------------------------+
-- 今天与 1/1/1900 相差多少周？
SELECT DATEDIFF(week, 0, GETDATE())
+------+
| 6217 |
+------+
-- 将第 6217 周加 0
SELECT DATEADD(week, DATEDIFF(week, 0, GETDATE()),0)
+-------------------------+
| 2019-02-25 00:00:00.000 |
+-------------------------+
现在轮到你来处理日期了！
SQL Server 中的函数与存储过程编写
