Adding a new column to an exisiting tbale sql

To add a new column to an existing table in SQL, you can use the ALTER TABLE statement. The basic syntax is:

ALTER TABLE table_name
ADD COLUMN new_column_name data_type;

Here:

• table_name is the name of the existing table you want to modify.
• new_column_name is the name of the new column you want to add.
• data_type is the data type of the new column (e.g. INT, VARCHAR, DATE, etc.).

For example, let's say you have a table called employees with the following columns:

+----+----------+--------+
| id | name     | salary |
+----+----------+--------+
| 1  | John     | 50000 |
| 2  | Jane     | 60000 |
| 3  | Joe      | 70000 |
+----+----------+--------+

You want to add a new column called department with a data type of VARCHAR(50). You can use the following SQL statement:

ALTER TABLE employees
ADD COLUMN department VARCHAR(50);

After running this statement, the employees table will have the new column:

+----+----------+--------+--------------+
| id | name     | salary | department   |
+----+----------+--------+--------------+
| 1  | John     | 50000 | Sales        |
| 2  | Jane     | 60000 | Marketing    |
| 3  | Joe      | 70000 | IT           |
+----+----------+--------+--------------+

Note that you can also specify additional options when adding a new column, such as:

• DEFAULT value: sets a default value for the new column.
• NULL or NOT NULL: specifies whether the new column can contain null values.
• UNIQUE or PRIMARY KEY: specifies whether the new column is unique or a primary key.

For example:

ALTER TABLE employees
ADD COLUMN department VARCHAR(50) DEFAULT 'Unknown';

This would set the default value of the department column to 'Unknown' for any new rows inserted into the table.