sqlserver- custom function

There are several sqlserver custom function in the
scalar-valued function (type of return value to determine a)
the scalar value one can think of the scalar mathematics (not only the magnitude direction) and a vector (direction while the size), Finally, I guess right, ha ha!
Table-valued function (returned as a table value corresponding to a parameterized view)
multi-statement table-valued function bound (scalar and inline table-valued function body, the return value is a list, and scalar functions, can use begin ... end)
hands:
first put forward a table

CREATE TABLE [dbo].[test](
	[keyid] [int] IDENTITY(1,1) NOT NULL,
	[sort] [varchar](10) NULL,
	[qty] [int] NULL,
	[aaa] [nvarchar](max) NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

Discharge point data into

a, scalar-valued function

create function F_Get(@@CustomKeyID int)  --@@CustomKeyID 参数
returns varchar(50)    --返回的类型text, 这里是 returns
as
begin
declare @res varchar(50)='';  --申明返回,并初始化

select  @res =[sort]   from test where   [keyid] =@@CustomKeyID  --写好sql

return  @res; 
end

调用
SELECT [dbo].F_Get(5) as [名字] 
 ---调用时候最好写上[dbo]，通过数据库对象去调用，不然会报错，找到不这个函数

Results:

2, the value of the function table

create  function F_GetTablea(@keyid int)
returns table  --返回table
as
return ( select * from [dbo].[test] where [keyid]=@keyid )    --括弧里面返回一个数据表的查询

select * from dbo.F_GetTablea(5)  --调用

Results:

3, multi-statement table-valued function

create function F_gettest(@cuseID int)
returns  @cuestable table   --字段需要和原表字段名称类型都相同，
(
[keyid] int,
[sort] varchar(10)
)
as
begin
    
  if (@cuseID%2 =0)
  begin
    insert  into @cuestable select [keyid] ,[sort] from [dbo].[test] where   [keyid]  =1       
  end
  else
  begin
    insert  into @cuestable select [keyid] ,[sort] from [dbo].[test] where   [keyid] =6  
  end 
  
 return  --这个不能删除，一种语法结构
end

The results

temporarily write to you, welcome advice!