Dropping a Column : Alter Table « Table « Oracle PL/SQL Tutorial

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Oracle PL/SQL Tutorial » Table » Alter Table 
6. 3. 16. Dropping a Column
SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /

Table created.

SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ('01','Jason',    'Martin',  to_date('19960725','YYYYMMDD'), to_date('20060725','YYYYMMDD'), 1234.56'Toronto',  'Programmer')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('02','Alison',   'Mathews', to_date('19760321','YYYYMMDD'), to_date('19860221','YYYYMMDD'), 6661.78'Vancouver','Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('03','James',    'Smith',   to_date('19781212','YYYYMMDD'), to_date('19900315','YYYYMMDD'), 6544.78'Vancouver','Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('04','Celia',    'Rice',    to_date('19821024','YYYYMMDD'), to_date('19990421','YYYYMMDD'), 2344.78'Vancouver','Manager')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('05','Robert',   'Black',   to_date('19840115','YYYYMMDD'), to_date('19980808','YYYYMMDD'), 2334.78'Vancouver','Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('06','Linda',    'Green',   to_date('19870730','YYYYMMDD'), to_date('19960104','YYYYMMDD'), 4322.78,'New York',  'Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('07','David',    'Larry',   to_date('19901231','YYYYMMDD'), to_date('19980212','YYYYMMDD'), 7897.78,'New York',  'Manager')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('08','James',    'Cat',     to_date('19960917','YYYYMMDD'), to_date('20020415','YYYYMMDD'), 1232.78,'Vancouver', 'Tester')
  3  /

row created.

SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select from Employee
  2  /

ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester

rows selected.

SQL>
SQL> desc employee;
 Name             Null?    Type
 -----------------

 ID               NOT NULL VARCHAR2(4)
 FIRST_NAME                VARCHAR2(10)
 LAST_NAME                 VARCHAR2(10)
 START_DATE                DATE
 END_DATE                  DATE
 SALARY                    NUMBER(8,2)
 CITY                      VARCHAR2(10)
 DESCRIPTION               VARCHAR2(15)

SQL>
SQL> ALTER TABLE employee
  2  DROP COLUMN last_name;


SQL>
SQL> desc employee;
 Name             Null?    Type
 -----------------

 ID               NOT NULL VARCHAR2(4)
 FIRST_NAME                VARCHAR2(10)
 START_DATE                DATE
 END_DATE                  DATE
 SALARY                    NUMBER(8,2)
 CITY                      VARCHAR2(10)
 DESCRIPTION               VARCHAR2(15)

SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /

Table dropped.

SQL>
SQL>
6. 3. Alter Table
6. 3. 1. Altering a Table
6. 3. 2. Some of the aspects of a column you can modify using ALTER TABLE
6. 3. 3. Adding a Column
6. 3. 4. ADD initially_created DATE DEFAULT SYSDATE NOT NULL;
6. 3. 5. Changing the Size of a Column
6. 3. 6. Decrease the length of a column
6. 3. 7. Changing the Precision of a Numeric Column
6. 3. 8. Decrease the precision of a numeric column
6. 3. 9. Changing the Data Type of a Column
6. 3. 10. Fill data into new added table column
6. 3. 11. Changing the Default Value of a Column
6. 3. 12. Alter table to add new constraint for new added column
6. 3. 13. ALTER TABLE to DISABLE a CONSTRAINT
6. 3. 14. Alter table to add primary key
6. 3. 15. Alter table to add primary key across more than one columns
6. 3. 16. Dropping a Column
6. 3. 17. New added columns are empty
6. 3. 18. Alter table to add unique with tablespace and storage setting
6. 3. 19. Alter table to add primary key with tablespace and storage setting
6. 3. 20. alter table nologging
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