SQL take just the numeric values from a varchar

Say i have a few fields like the following:

abd738927
jaksm234234
hfk342
ndma0834
jon99322

Type: varchar.

How do I take just the numeric values from this to display:

738927
234234
342
0834
99322

Have tried substring however the data varies in length, and cast didnt work either due to being unable to convert, any ideas?

Here's the example with PATINDEX:

select SUBSTRING(fieldName, PATINDEX('%[0-9]%', fieldName), LEN(fieldName))

This assumes (1) the field WILL have a numeric, (2) the numerics are all grouped together, and (3) the numerics don't have any subsequent characters after them.

Extract only numbers (without using while loop) and check each and every character to see if it is a number and extract it

   Declare @s varchar(100),@result varchar(100)
    set @s='as4khd0939sdf78' 
    set @result=''

    select
        @result=@result+
                case when number like '[0-9]' then number else '' end from 
        (
             select substring(@s,number,1) as number from 
            (
                select number from master..spt_values 
                where type='p' and number between 1 and len(@s)
            ) as t
        ) as t 
    select @result as only_numbers 

DECLARE @NonNumeric varchar(1000) = 'RGI000Testing1000'
DECLARE @Index int  
SET @Index = 0  
while 1=1  
begin  
    set @Index = patindex('%[^0-9]%',@NonNumeric)  
    if @Index <> 0  
    begin  
        SET @NonNumeric = replace(@NonNumeric,substring(@NonNumeric,@Index, 1), '')  
    end  
    else    
        break;   
end     
select @NonNumeric -- 0001000

I think you're wanting VBA's Val() function. Easy enough to accomplish with IsNumeric()

create function Val 
(
    @text nvarchar(40)
) 
returns float
as begin
    -- emulate vba's val() function
    declare @result float 
    declare @tmp varchar(40)

    set @tmp = @text
    while isnumeric(@tmp) = 0 and len(@tmp)>0 begin
        set @tmp=left(@tmp,len(@tmp)-1)
    end
    set @result = cast(@tmp as float)

    return @result
end