How to Add Column in Existing Table in Oracle

ALTER TABLE in SQL helps to change the values in a pre-existing table in the database. Alteration can be done:

1. To add a new column
2. To delete or drop column
3. To modify the column 
4. To rename a column
5. To rename a table

1. Oracle Alter Add a single column

Syntax

ALTER TABLE table_name
ADD(column_name datatype(size));

• ALTER TABLE is the keyword used to apply changes in table.
• ALTER TABLE with ADD is used to add a column in an existing table.
• column_name is the name of the column we want to add.

Example

Now, to know the Ranking of students, we need to enter a column Marks in the Stu table:

ALTER TABLE Stu
ADD(Marks number(20));

Output:

2. Oracle Add multiple columns in Existing Table

ALTER TABLE table_name
ADD(column1_name datatype(size),
column2_name datatype(size),
column3_name datatype(size)....);

For example, we need to add 2 more columns containing maximum marks and the last name of the student. 

Output:

After executing Select query, we will find the output that is below:

It is showing null values because as of now we have not updated values in the newly created columns.