How to generate alpha number values from a sql query? - sql

Question

I am using the below in my stored procedure to create a 8 digit password and return it as output.
select #AuthKey = #AuthKey + char(n) from
(
select top 8 number as n from master.. spt_values
where type= 'p' and number between 48 and 57
order by newid()
) as t
But i want the output as alpha numeric value, instead of just numeric value. How can i get it ?

Answer 1

Anuya -- this is a very clever way to randomize values, using order by newid(). You can also use lowercase characters, if your passwords are case sensitive:
declare #AuthKey varchar(255)
set #AuthKey = ''
select #AuthKey = #AuthKey + char(n) from
(
select top 8 number as n
from master..spt_values
where type= 'p' and (
(number between 48 and 57) -- numbers
or (number between 65 and 90) -- uppercase letters
or (number between 97 and 122) -- lowercase letters
)
order by newid()
) as t
print #AuthKey
Using a slightly different approach, you could include a specific character set, including symbols:
declare #AuthKey varchar(255), #chars varchar(255), #len int
set #AuthKey = ''
set #chars = '012345ACDFGIJKLMSTXYZ_-##!'
set #len = len(#chars)
select #AuthKey = #AuthKey + chr.c
from (
select substring(#chars, num.n, 1) as c
from (
select top 8 number as n
from master..spt_values
where type='p' and (number between 1 and #len)
order by newid()
) as num
) as chr
print #AuthKey
Of course this only includes any given character one time. Still it is a very clever way of generating passwords. Kudos!
Edit:
If you want to have the chance of having doubles, you can do it like this :
declare #AuthKey varchar(255), #chars varchar(255), #len int
set #AuthKey = ''
set #chars = '012345ACDFGIJKLMSTXYZ_-##!'
set #len = len(#chars)
SELECT TOP 8 #AuthKey = #AuthKey + SubString(#chars, 1 + Convert(int, ABS(BINARY_CHECKSUM(NewID())) % #len), 1)
FROM master..spt_values
(will be slightly faster too as the query doesn't require sorting spt_values.