Question

Why do in SQL*PLUS we have SET SCAN and SET DEFINE both ?
I know both are used interchangeably in SQL.
I tested and found that if i set any of them OFF, substitution variables will not work.
Is their any specific case where we need both and importance of both can be understood simultaneously?

Thanks in advance.

Answer 1

SET DEFINE is more flexible as it lets you change the substitution character from & to something else, whereas SET SCAN can only be turned on or off.

Probably more importantly, SET SCAN is obsolete; from the documentation:

Obsolete commands are available in current releases of SQL*Plus. In
future releases, they may only be available by setting the
SQLPLUSCOMPATIBILITY variable. You should modify scripts using
obsolete commands to use the alternative commands.

So both work for now, but I wouldn’t use SET SCAN in any new code.