Substitution variables in Sql*Plus

Question

Hi all,
How to make Sql*Plus ask for the substitution variable value one time only for a substitution variable even if it appears multiple times inside a query ? Because so far each time I launched the query below then I have been asked two times by Sql*Plus for the variable value. For example : select ref_site from t_comsis where longitude_lamb + latitude_lamb < &distance + power(&distance,2).
Thanks

Answer 1

of course accept is more friendly, you can check for valid number, you can have a prompt or a hidden input.
you can also undef your variable if you prefer the && solution
SQL> select &&x+&&x from dual;
Enter value for x: 1
old   1: select &&x+&&x from dual
new   1: select 1+1 from dual
       1+1
         2
SQL> undef x
SQL> r
  1* select &&x+&&x from dual
Enter value for x: 2
old   1: select &&x+&&x from dual
new   1: select 2+2 from dual
       2+2
         4