Adding two columns in SQL

In SQL, adding two columns to a table involves using the ALTER TABLE statement. The ALTER TABLE statement is used to modify an existing table structure by adding, modifying, or dropping columns.


Here’s a general syntax for adding two columns to an existing table:

ALTER TABLE your_table_name
ADD column1_name datatype,
    column2_name datatype;

Let’s break down the syntax:

your_table_name: Replace this with the actual name of the table to which you want to add columns.

column1_name: Specify the name of the first column you want to add.

datatype: Specify the data type for the first column (e.g., INT, VARCHAR(50), DATE, etc.).

column2_name: Specify the name of the second column you want to add.

datatype: Specify the data type for the second column.


Here’s an example to illustrate the process. Let’s say we have a table called “Employees,” and we want to add two columns: “Salary” (datatype: DECIMAL) and “HireDate” (datatype: DATE).

    HireDate DATE;

After executing this SQL statement, the “Employees” table will have two new columns, “Salary” and “HireDate.”

Make sure to choose appropriate data types and lengths based on the kind of data you intend to store in these new columns. Additionally, keep in mind that modifying a table in a production database should be done with caution, especially if there is existing data in the table. Always have a backup of your database before making structural changes to ensure data integrity.