Posted by A cool new feature in 12c is the ability to make a column invisible. The concept has existed since 8i to handle things like “set unused” and function based indexes, but now it is available to developers directly.
SQL> create table T ( c1 int, c2 int );
Table created.
SQL> desc T
Name Null? Type
----------------------------- -------- -----------------
C1 NUMBER(38)
C2 NUMBER(38)
SQL> alter table T modify c2 invisible;
Table altered.
SQL> desc T
Name Null? Type
----------------------------- -------- -----------------
C1 NUMBER(38)
So at this point… how I can tell in SQL Plus that I even have an invisible column, without querying the data dictionary.
It’s easy, we have a new setting – COLINVISIBLE
SQL> set colinvisible on
SQL> desc T
Name Null? Type
----------------------------- -------- -----------------
C1 NUMBER(38)
C2 (INVISIBLE) NUMBER(38)
Of course, if you want to play a practical joke on your work colleagues, you could do this:
SQL> desc t
Name Null? Type
----------------------------- -------- -------------
C1 NUMBER(38)
C2 (INVISIBLE) DATE
C2 (INVISIBLE) NUMBER(38)
Learning is not a spectator sport 
Hi Connor,
I don’t get it. How did you get the result below?)
Name Null? Type
—————————– ——– ————-
C1 NUMBER(38)
C2 (INVISIBLE) DATE
C2 (INVISIBLE) NUMBER(38)
I have achieved only this:
SQL> create table t (c1 int, c2 int);
Table T created.
SQL> desc t;
Name Null? Type
—- —– ———-
C1 NUMBER(38)
C2 NUMBER(38)
SQL> alter table t modify c2 invisible;
Table T altered.
SQL> set colinvisible on;
SQL> desc t;
Name Null? Type
————– —– ———-
C1 NUMBER(38)
C2 (INVISIBLE) NUMBER(38)
SQL> alter table t set unused column c2;
Table T altered.
SQL> alter table t add c2 date;
Table T altered.
SQL> alter table t modify c2 invisible;
Table T altered.
SQL> desc t;
Name Null? Type
————————————– —– ———-
C1 NUMBER(38)
C2 (INVISIBLE) DATE
SYS_C00002_20040909:23:36$ (INVISIBLE) NUMBER(38)
SQL> drop table t purge;
Table T dropped.
You create a column called “C2 (INVISIBLE)” 🙂
Yeah, I got you. That’s pretty sneaky. 🙂