ORACLE - Delete ASM datafiles

How to delete ASM files for a database ?

spool file.txt
COL gsql FORMAT a300
SET ECHO OFF
SET VERIFY OFF
SET HEADING OFF
SET FEEDBACK OFF
SET PAGESIZE 0
SET LINESIZE 600
SET TRIMSPOOL ON
spool del_asm.sql
SELECT 'ALTER DISKGROUP '||gname||' DROP FILE '''||full_path||''';' gsql FROM
(SELECT CONCAT('+'||gname, SYS_CONNECT_BY_PATH(aname,'/')) full_path, gname FROM
(SELECT g.name gname, a.parent_index pindex, a.name aname,
a.reference_index rindex, a.ALIAS_DIRECTORY adir
FROM v$asm_alias a, v$asm_diskgroup g
WHERE a.group_number = g.group_number)
WHERE adir='N'
START WITH (MOD(pindex, POWER(2, 24))) = 0
CONNECT BY PRIOR rindex = pindex)
WHERE full_path LIKE UPPER('%&database1%');
spool off