error ORA-00998: must name this expression with a column alias - oracle

Question

I tried to create table from all_tab_columns but it throws me an error.
like error ORA-00998: must name this expression with a column alias.
i tried to figure it out but not working.
Declare
CURSOR c1 IS
SELECT COLUMN_NAME FROM (select 'standard_hash(MY_NAME) AS MY_NAME' COLUMN_NAME from DUAL
UNION
SELECT COLUMN_NAME FROM ALL_TAB_COLUMNS WHERE TABLE_NAME='TABLE1' AND COLUMN_NAME<>'MY_NAME');
cols c1%ROWTYPE;
sqlstmt VARCHAR2(4000);
BEGIN
OPEN c1;
LOOP
FETCH c1 into cols;
EXIT WHEN c1%NOTFOUND;
sqlstmt := sqlstmt ||cols.column_name||',';
END LOOP;
CLOSE c1;
sqlstmt := 'CREATE TABLE TABLE2 AS SELECT '||substr(sqlstmt, 1, length(sqlstmt)-1)||' FROM TABLE1';
DBMS_OUTPUT.PUT_LINE(sqlstmt);
EXECUTE IMMEDIATE sqlstmt;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('error '||sqlerrm);
END;
/

Answer 1

You just have to give the name to the expression as follows:
sqlstmt := 'CREATE TABLE TABLE2 AS SELECT '
||substr(sqlstmt, 1, length(sqlstmt)-1)
||' as column_name FROM TABLE1'; -- column_name will bre name of the column of new table
As it will become the name of the column of newly created table.

Answer 2

I think this can be simplified somewhat.
You don't need to declare an explicit cursor and a record type and fetch each row into it, as this is already built into the language as the Cursor FOR loop construction:
declare
sqlStmt long := 'create table table2 as select ';
begin
for r in (
select 'standard_hash(my_name) as my_name' column_name
from dual
union
select column_name
from all_tab_columns
where table_name = 'TABLE1'
and column_name <> 'MY_NAME'
)
loop
sqlStmt := sqlStmt || r.column_name || ', ';
end loop;
sqlStmt := sqlStmt || rtrim(sqlStmt,', ') || ' from table1';
dbms_output.put_line(sqlStmt);
execute immediate sqlStmt;
end;
/
But you can do this without any loop, as the listagg function can already build a comma-separated list for you. It also makes it easier to retain the order of columns in the original table.
declare
selectList long;
sqlStmt long;
begin
select listagg(
case column_name
when 'MY_NAME' then 'standard_hash(my_name) as my_name'
else lower(column_name)
end, ', '
) within group (order by column_id) as select_list
into selectList
from user_tab_columns c
where c.table_name = 'TABLE1';
sqlStmt :=
'create table table2 pctfree 0 nologging parallel as '||chr(10)||
'select '||selectList||chr(10)||
'from table1';
dbms_output.put_line(sqlStmt||';');
execute immediate sqlstmt;
end;