日期操作
在 SQL Server 中撰寫函式與預存程序
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 語法：
DATEADD (datepart, number, date)
-- 依 data_type 傳回對應的表達式
-- 2019/2/27 的隔天
SELECT DATEADD(day, 1, '2/27/2019')
+-------------------------+
| 2019-02-28 00:00:00.000 |
+-------------------------+
DATEADD 與 GETDATE
-- 昨天
SELECT DATEADD(d, -1, GETDATE())
+-------------------------+
| 2019-02-26 09:20:50.013 |
+-------------------------+
-- 昨日計程車載客數
SELECT SUM(PassengerCount)
FROM YellowTripData
WHERE CAST(PickupDate as date) = DATEADD(d, -1, GETDATE())
還記得 DATEDIFF 嗎？
SELECT DATEDIFF(day, '2/27/2019', '2/28/2019')
+---+
| 1 |
+---+
SELECT DATEDIFF(year, '12/31/2017', '1/1/2019')
+---+
| 2 |
+---+
-- 本週第一天
SELECT DATEADD(week, DATEDIFF(week, 0, GETDATE()), 0)
-- 第一步
GETDATE()
+-------------------------+
| 2019-02-27 10:33:39.713 |
+-------------------------+
-- 今天到 1/1/1900 相隔幾週？
SELECT DATEDIFF(week, 0, GETDATE())
+------+
| 6217 |
+------+
-- 在第 6217 週加上 0
SELECT DATEADD(week, DATEDIFF(week, 0, GETDATE()),0)
+-------------------------+
| 2019-02-25 00:00:00.000 |
+-------------------------+
換你來做日期操作了！
在 SQL Server 中撰寫函式與預存程序
