Sunday, November 25, 2012

SQL Query Add new Column Existing Table

The SQL ALTER TABLE statement allows you to rename an existing table. It can also be used to add, modify, or drop a column from an existing table.

SQL ALTER TABLE - Renaming a table

To rename a table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  RENAME TO new_table_name;
For example:
ALTER TABLE suppliers
  RENAME TO vendors;
This will rename the suppliers table to vendors.

SQL ALTER TABLE - Adding column(s) to a table

Syntax #1
To add a column to an existing table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  ADD column_name column-definition;
For example:
ALTER TABLE supplier
  ADD supplier_name varchar2(50);
This will add a column called supplier_name to the supplier table.



Syntax #2
To add multiple columns to an existing table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  ADD (column_1 column-definition,
       column_2 column-definition,
       ...
       column_n column_definition);
For example:
ALTER TABLE supplier
  ADD (supplier_name varchar2(50),
       city varchar2(45));
This will add two columns (supplier_name and city) to the supplier table.

SQL ALTER TABLE - Modifying column(s) in a table

Syntax #1
To modify a column in an existing table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  MODIFY column_name column_type;
For example:
ALTER TABLE supplier
  MODIFY supplier_name varchar2(100) not null;
This will modify the column called supplier_name to be a data type of varchar2(100) and force the column to not allow null values.

Syntax #2
To modify multiple columns in an existing table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  MODIFY (column_1 column_type,
          column_2 column_type,
          ...
          column_n column_type);
For example:
ALTER TABLE supplier
  MODIFY (supplier_name varchar2(100) not null,
          city varchar2(75));
This will modify both the supplier_name and city columns.

SQL ALTER TABLE - Drop column(s) in a table

Syntax #1
To drop a column in an existing table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  DROP COLUMN column_name;
For example:
ALTER TABLE supplier
  DROP COLUMN supplier_name;
This will drop the column called supplier_name from the table called supplier.

SQL ALTER TABLE - Rename column(s) in a table
(NEW in Oracle 9i Release 2)

Syntax #1
Starting in Oracle 9i Release 2, you can now rename a column.
To rename a column in an existing table, the SQL ALTER TABLE syntax is:
ALTER TABLE table_name
  RENAME COLUMN old_name to new_name;
For example:
ALTER TABLE supplier
  RENAME COLUMN supplier_name to sname;
This will rename the column called supplier_name to sname.

Practice Exercise #1:

Based on the departments table below, rename the departments table to depts.
CREATE TABLE departments
( department_id number(10) not null,
  department_name varchar2(50) not null,
  CONSTRAINT departments_pk PRIMARY KEY (department_id)
);

Solution:

The following SQL ALTER TABLE statement would rename the departments table to depts:
ALTER TABLE departments
  RENAME TO depts;

Practice Exercise #2:

Based on the employees table below, add a column called salary that is a number(6) datatype.
CREATE TABLE employees
( employee_number number(10) not null,
  employee_name varchar2(50) not null,
  department_id number(10),
  CONSTRAINT employees_pk PRIMARY KEY (employee_number)
);

Solution:

The following SQL ALTER TABLE statement would add a salary column to the employees table:
ALTER TABLE employees
  ADD salary number(6);

Practice Exercise #3:

Based on the customers table below, add two columns - one column called contact_name that is a varchar2(50) datatype and one column called last_contacted that is a date datatype.
CREATE TABLE customers
( customer_id number(10) not null,
  customer_name varchar2(50) not null,
  address varchar2(50),
  city varchar2(50),
  state varchar2(25),
  zip_code varchar2(10),
  CONSTRAINT customers_pk PRIMARY KEY (customer_id)
);

Solution:

The following SQL ALTER TABLE statement would add the contact_name and last_contacted columns to the customers table:
ALTER TABLE customers
  ADD (contact_name varchar2(50),
       last_contacted date);

Practice Exercise #4:

Based on the employees table below, change the employee_name column to a varchar2(75) datatype.
CREATE TABLE employees
( employee_number number(10) not null,
  employee_name >varchar2(50) not null,
  department_id number(10),
  CONSTRAINT employees_pk PRIMARY KEY (employee_number)
);

Solution:

The following SQL ALTER TABLE statement would change the datatype for the employee_name column to varchar2(75):
ALTER TABLE employees
  MODIFY employee_name varchar2(75);

Practice Exercise #5:

Based on the customers table below, change the customer_name column to NOT allow null values and change the state column to a varchar2(2) datatype.
CREATE TABLE customers
( customer_id number(10) not null,
  customer_name varchar2(50),
  address varchar2(50),
  city varchar2(50),
  state varchar2(25),
  zip_code varchar2(10),
  CONSTRAINT customers_pk PRIMARY KEY (customer_id)
);

Solution:

The following SQL ALTER TABLE statement would modify the customer_name and state columns accordingly in the customers table:
ALTER TABLE customers
  MODIFY (customer_name varchar2(50) not null,
          state varchar2(2));

Practice Exercise #6:

Based on the employees table below, drop the salary column.
CREATE TABLE employees
( employee_number number(10) not null,
  employee_name varchar2(50) not null,
  department_id number(10),
  salary number(6),
  CONSTRAINT employees_pk PRIMARY KEY (employee_number)
);

Solution:

The following SQL ALTER TABLE statement would drop the salary column from the employees table:
ALTER TABLE employees
  DROP COLUMN salary;

Practice Exercise #7:

Based on the departments table below, rename the department_name column to dept_name.
CREATE TABLE departments
( department_id number(10) not null,
  department_name varchar2(50) not null,
  CONSTRAINT departments_pk PRIMARY KEY (department_id)
);

Solution:

The following SQL ALTER TABLE statement would rename the department_name column to dept_name in the departments table:
ALTER TABLE departments
  RENAME COLUMN department_name to dept_name;

4 comments:

  1. hi assma i want convert arabic num to words in crystal report can you help me plzz
    this function convert numz to english words
    towords({table.field})
    im waiting for solution plz

    ReplyDelete
  2. ASMA plz im waiting for help

    ReplyDelete
  3. Hi,

    you can use the below of my Article , hop it will help you

    How to display arabic numbers in crystal reports

    http://asmaqureshi.blogspot.com/2010/06/how-to-display-arabic-numbers-in.html

    ReplyDelete
  4. مش ده قصدى كده
    مثلا 150
    تكون
    مائة وخمسون فقط

    ReplyDelete