--set @str='abcd'
set @sql='select code from '+@table+' where (len(code)=1 and code like left('+''''+@str+''',1))'
set @i=2
while @i<= len(@str)
begin
set @sql=@sql+' or (len(code)='+cast(@i as char(2))+' and code like left('+''''+@str+''','+cast(@i as char(2))+'))'
set @i=@i+1
end
exec( @sql)