declare
p_table varchar2(255):='DATENBANK';
p_col varchar(255);
p_num number(10);
p_type varchar2(255):='varchar2(255)';

begin
p_num := 'select count(*) from user_tab_columns where table_name = (' || p_table || ')';
p_col := ' t '+' to_char(p_num, '9999.9') ';
EXECUTE IMMEDIATE 'ALTER TABLE ' || p_table || ' add (' || p_col || ' ' || p_type || ')';
end;


Warum bekomme ich hier immer die Fehlermeldung?

AJAX call returned server error ORA-06502: PL/SQL: numeric or value error: character to number conversion error for Execute PL/SQL Code.