How can the structure of an existing table be modified in MySQL?

To change the structure of an existing table, you can use the ALTER TABLE statement in MySQL.

The grammar is as follows:

ALTER TABLE table_name
ADD COLUMN column_name data_type;

ALTER TABLE table_name
DROP COLUMN column_name;

ALTER TABLE table_name
MODIFY COLUMN column_name new_data_type;

ALTER TABLE table_name
CHANGE COLUMN column_name new_column_name new_data_type;

Among them:

1. ADD COLUMN: A command used to add a new column to a table.
2. DROP COLUMN: Used to remove a column from a table.
3. Modify Column: Used to change the data type of a column.
4. CHANGE COLUMN: Used to alter the name and data type of a column.

For example, to add a new column to the table, you can use the following statement:

ALTER TABLE users
ADD COLUMN age INT;

To delete a column in a table, you can use the following statement:

ALTER TABLE users
DROP COLUMN age;

To change the data type of a column in a table, you can use the following statement:

ALTER TABLE users
MODIFY COLUMN age VARCHAR(50);

To change the name and data type of a column in a table, you can use the following statement:

ALTER TABLE users
CHANGE COLUMN age new_age INT;

Please choose the appropriate ALTER TABLE statement to modify the structure of an existing table as needed.