What SQL command is used to add a new column to an existing table?

The SQL command used to add a new column to an existing table is the ALTER TABLE command. Here is a step-by-step guide on how to use it:

1. First, you need to know the name of the table you want to alter. Let's assume the table name is 'Students'.

2. Decide on the name and data type of the new column you want to add. Let's say we want to add a column named 'Email' of type 'VARCHAR(100)'.

3. Now, you can construct the SQL command. The general syntax is:

   ALTER TABLE table_name ADD column_name column_type;

4. Substituting in our specific values, the command becomes:

   ALTER TABLE Students ADD Email VARCHAR(100);

5. You can now run this command in your SQL environment to add the new column to the 'Students' table.

Remember to replace 'Students', 'Email', and 'VARCHAR(100)' with your actual table name, column name, and column type.