How to add new column to existing table in sql

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

ALTER TABLE table_name
ADD column_name data_type;

Here:

• table_name is the name of the table you want to modify.
• column_name is the name of the new column you want to add.
• data_type is the data type of the new column.

For example, to add a new column named age with a data type of int to a table named employees, you would use the following SQL statement:

ALTER TABLE employees
ADD age int;

If you want to add a column with a default value, you can use the following syntax:

ALTER TABLE table_name
ADD column_name data_type DEFAULT default_value;

For example, to add a new column named salary with a data type of float and a default value of 0.0 to a table named employees, you would use the following SQL statement:

ALTER TABLE employees
ADD salary float DEFAULT 0.0;

If you want to add a column with a constraint, such as a primary key or foreign key, you can use the following syntax:

ALTER TABLE table_name
ADD column_name data_type PRIMARY KEY;

For example, to add a new column named employee_id with a data type of int and set it as the primary key to a table named employees, you would use the following SQL statement:

ALTER TABLE employees
ADD employee_id int PRIMARY KEY;

Note that you can only add a column to the end of the table. If you want to add a column in a specific position, you can use the ADD COLUMN statement with the AFTER or BEFORE clause.

For example, to add a new column named department with a data type of varchar(50) after the name column in a table named employees, you would use the following SQL statement:

ALTER TABLE employees
ADD COLUMN department varchar(50) AFTER name;

Similarly, to add a new column named job_title with a data type of varchar(50) before the name column in a table named employees, you would use the following SQL statement:

ALTER TABLE employees
ADD COLUMN job_title varchar(50) BEFORE name;

Remember to replace table_name, column_name, and data_type with your actual table and column names, and default_value with the default value you want to set for the column.