日期时间变量

SQL Server 中的函数与存储过程编写

Meghan Kwartler

IT Consultant

储物柜

-- 声明变量并赋初值
 DECLARE @StartTime as time = '08:00 AM'

-- 先 DECLARE 变量，再 SET 值
DECLARE @StartTime AS time 
SET @StartTime = '08:00 AM'

-- 先 DECLARE 变量，再 SET 值
DECLARE @BeginDate as date 
SET 
  @BeginDate = (
    SELECT TOP 1 PickupDate 
    FROM YellowTripData 
    ORDER BY PickupDate ASC
  );

CAST 转换

-- CAST 语法
CAST ( expression AS data_type [ ( length ) ] ) 
-- 按 data_type 返回 expression

-- 声明 datetime 变量
-- 在 CAST 时将 @BeginDate 和 @StartTime 赋值
DECLARE @StartDateTime as datetime 
SET @StartDateTime = CAST(@BeginDate as datetime) + CAST(@StartTime as datetime)

-- 声明含两列的表变量
DECLARE @TaxiRideDates TABLE(
    StartDate date,
    EndDate date)

-- 向表变量插入静态值
INSERT INTO @TaxiRideDates (StartDate, EndDate)
SELECT '3/1/2018', '3/2/2018'

-- 插入查询结果
INSERT INTO @TaxiRideDates(StartDate, EndDate)
SELECT DISTINCT
    CAST(PickupDate  as date), 
    CAST(DropOffDate  as date)
    FROM YellowTripData;

轮到您：DECLARE、SET、CAST 和 INSERT！

SQL Server 中的函数与存储过程编写