Question

i want to write a UDF which uses String Value and starting index number and count number like that:

GetValueUDF(“i am 18 years old.”,6,2) output: 18 , 6: .nth starting point, 2: count

GetValueUDF(“i am 101 years old.”,6,3) output: 101

GetValueUDF(“i am 101 years old.”,1,4) output: “i am”

Answer 1

I am not quite sure why you want to create a user defined function for this since that is what the substring function does. But you should be able to use something like the following:

create function GetValueUDF
(
  @string varchar(max), 
  @startPosition int,
  @length int
)
returns varchar(max)
as

begin
  return substring(@string, @startPosition, @length)
end

See SQL Fiddle with Demo