--字串功能
--substring
print substring('iamagoodperson',1,5)
select substring('iamagoodperson',1,5)
--upper
select upper('he is a good person')
--lower
select LOWER('this is an VERY interesting job')
--ltrim
select ltrim(' i am a good person')
--rtrim
select rtrim(' heihei,i do not know why it likes this ')
--replace
select replace('iwanttoaskyou','ttoa','i love you')
--stuff
select stuff('我的名字是朱旭傑',6,8,'summer')
--Date/Time Fuction
--getdate()
select getdate() as 'today'
--dateadd()
select dateadd(yy,10,getdate())
--datediff()
select datediff(yy,'1982/5/3',getdate()) as
--datepart()
select datepart(dw,getdate())
select datepart(yy,getdate())
select datepart(mm,getdate())
select datepart(dd,getdate())
select datepart(ss,getdate())
select datepart(ms,getdate())
select datepart(dd,'1982/5/3')
print datepart(dw,'1982/8/22')
--day(),相當於datepart(dd,時間)
select day('1982/5/3')
select day(getdate())
--month(),相當於datepart(mm,時間)
select month(getdate())
--year(),相當於datepart(yy,時間)
select year(getdate())
--數學函數
--abs()
select abs(-100.3456)
--sin()
select sin(0.54)
--cos()
select cos(3.14)
--power()
select power(10,2)
--round 返回數字運算式並四捨五入為指定的長度或精度
select round(100.45,1)
select round(123,45,-2)
--floor()
select floor(4.9)
select floor(-123.99)
--ceiling()
select ceiling(4.9)
select ceiling(-123.99)
--sqrt()
select sqrt(100)
--square
select square(10)
select square(-15)
--轉換函式
--cast()
select cast(100.45 as int)
select cast(1345 as varchar(10))
--convert()
select convert(int,100.56)
select convert(varchar(10),2345)
--空值函數
--isnull()
declare @temp_table table
(
bookID VARCHAR(10) primary key,
book_price float default null,
bookName varchar(50)
)
insert into @temp_table values('1',50,'c#')
insert into @temp_table values('2',null ,'c')
select bookID AS '書的編號',isnull(book_price,0) as '書的價格'
from @temp_table
--nullif(),只要參數裡的兩個運算式相同就返回null
select nullif('iam','iam')
--coalesce返回其參數中第一個非空運算式
select coalesce(null,null,'i am a good boy')#資料庫技術
