What commands can modify the structure of a table in SQL?

To modify the structure of a table in SQL, the ALTER TABLE command is used. With it, you can:

• Add new columns: ALTER TABLE table_name ADD column_name datatype;
• Drop columns (in some DBMS): ALTER TABLE table_name DROP COLUMN column_name;
• Change the data type of a column: ALTER TABLE table_name MODIFY column_name new_datatype;
• Rename columns or tables (depends on the DBMS)

Example:

ALTER TABLE employees ADD salary DECIMAL(10,2);
ALTER TABLE employees DROP COLUMN age;
ALTER TABLE employees MODIFY salary FLOAT;