Query Select Oracle PLSQL Tutorial

SQL>
SQL> CREATE TABLE promotion(
  2    title_id     CHAR(3)      NOT NULL,
  3    advance      DECIMAL(9,2) NULL    ,
  4    royalty_rate DECIMAL(5,2) NULL);
Table created.
SQL>
SQL> INSERT INTO promotion VALUES('T01',10000,0.05);
1 row created.
SQL> INSERT INTO promotion VALUES('T02',1000,0.06);
1 row created.
SQL> INSERT INTO promotion VALUES('T03',15000,0.07);
1 row created.
SQL> INSERT INTO promotion VALUES('T04',20000,0.08);
1 row created.
SQL> INSERT INTO promotion VALUES('T05',100000,0.09);
1 row created.
SQL> INSERT INTO promotion VALUES('T06',20000,0.08);
1 row created.
SQL> INSERT INTO promotion VALUES('T07',1000000,0.11);
1 row created.
SQL> INSERT INTO promotion VALUES('T08',0,0.04);
1 row created.
SQL> INSERT INTO promotion VALUES('T09',0,0.05);
1 row created.
SQL> INSERT INTO promotion VALUES('T10',NULL,NULL);
1 row created.
SQL> INSERT INTO promotion VALUES('T11',100000,0.07);
1 row created.
SQL> INSERT INTO promotion VALUES('T12',50000,0.09);
1 row created.
SQL> INSERT INTO promotion VALUES('T13',20000,0.06);
1 row created.
SQL>
SQL> SELECT title_id,
  2         -advance AS "Advance"
  3    FROM promotion;
TIT    Advance
--- ----------
T01     -10000
T02      -1000
T03     -15000
T04     -20000
T05    -100000
T06     -20000
T07   -1000000
T08          0
T09          0
T10
T11    -100000
TIT    Advance
--- ----------
T12     -50000
T13     -20000
13 rows selected.
SQL>
SQL> drop table promotion;
Table dropped.
SQL>