How to select from text list randomly? - sql

Question

I'm trying to build SQL function that I can use as a default value for a column. The function is about selecting an avatar image path randomly if the user didn't assign an image.
I have tried to but a completely wrong example to just approach the image not the solution
what I need to do is something like this
select top 1 from "avatar1,png, avatar2,png, avatar3.png, avatar4.png, avatar5.png" order by rand();
and I will convert it to a function like this
CREATE FUNCTION dbo.ReturnAvatar()
RETURNS nvarchar(100)
AS
BEGIN
DECLARE #ret nvarchar(100);
SET #ret = (select top 1 from "avatar1,png, avatar2,png, avatar3.png, avatar4.png, avatar5.png" as tbl order by rand());
RETURN #ret;
END;
this is just to explain the idea that I'm not able to apply. I don't know if SQL server has something like this or not.

Answer 1

Here is one way:
CREATE VIEW getNewID AS SELECT newid() as new_id
CREATE FUNCTION dbo.ReturnAvatar()
RETURNS nvarchar(100)
AS
BEGIN
DECLARE #ret nvarchar(100);
SET #ret = (SELECT TOP 1 value
FROM
STRING_SPLIT('avatar1.png,avatar2.png,avatar3.png,avatar4.png,avatar5.png', ',')
ORDER BY (SELECT new_id FROM getNewID));
RETURN #ret;
END;
Note that your current CSV string of filenames does not seem proper, because comma does not indicate the start of the extension in either Windows or Linux. So, I have assumed dot everywhere. In addition, if you want to use STRING_SPLIT, you may only split on a single character. Therefore, I assume that comma will be the delimiter here.

Answer 2

You do not need to create a table at all. Simply put the number inside your string and choose the number randomly:
select 'avatar'+str(round(rand()*5+1,0))+'.png'
would be fine.
Put that into your function and you are all set.
rand() produces 0..1(excl.) so you can simply multiply it by 5 and add 1 to get your range of 1...5
Demo: http://sqlfiddle.com/#!18/9eecb/82866
Documentation:
ROUND ( numeric_expression , length [ ,function ] )
STR ( float_expression [, length [, decimal]])
rand(seed)
So essentially you could boil it down to:
select 'avatar'+ltrim(str(rand()*5+1,20,0))+'.png'
with
ltrim(string) taking care of the space

Answer 3

create function dbo.ReturnAvatar(#uid uniqueidentifier, #avatars int = 10)
returns varchar(100)
as
begin
return ('avatar' + cast(abs(checksum(#uid)) % isnull(abs(#avatars), 10)+1 as varchar(100)) + '.png')
end
go
create table myusers
(
username varchar(50),
theavatar varchar(100) default( dbo.ReturnAvatar(newid(), default))
);
insert into myusers(username)
select top (10000) 'user' + cast(row_number() over(order by(select null)) as varchar(50))
from master.dbo.spt_values as a
cross join master.dbo.spt_values as b;
go
select theavatar, count(*)
from myusers
group by theavatar;
go
drop table myusers;