Oracle PL/SQL/Table/Change Column Size

Alter table: Changes the size of a column

SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 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> -- display data in the table
SQL> select * from Employee
  2  /
no rows selected
SQL>
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> --Changes the size of the Salary column:
SQL>
SQL> ALTER TABLE Employee MODIFY (Salary number(11,2));
Table altered.
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(11,2)
 CITY                                                                                                   VARCHAR2(10)
 DESCRIPTION                                                                                            VARCHAR2(15)
SQL>
SQL>
SQL> select * from employee;
no rows selected
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>
SQL>
SQL>

Enlarge column width

 
SQL>
SQL>  create table t(
  2      id number,
  3      data varchar2(200) );
SQL>
SQL>
SQL>  Alter table t
  2    modify
  3    (
  4     id number,
  5     data varchar2(255)
  6    );

SQL>
SQL>  Alter table t
  2    ADD
  3    (
  4     data2 varchar2(100)
  5    );

SQL>
SQL>  drop table t;