Part 38: Modifying Tables: ALTER TABLE (Add, Rename, Drop Columns)

As applications evolve, table structures must change via ALTER TABLE.

1. Common ALTER Operations

-- 1. Add a new column with a default value:
ALTER TABLE users ADD COLUMN phone_number VARCHAR(20);

-- 2. Rename a column:
ALTER TABLE users RENAME COLUMN first_name TO given_name;

-- 3. Modify data type or nullability:
ALTER TABLE users ALTER COLUMN phone_number SET NOT NULL;

-- 4. Drop a column:
ALTER TABLE users DROP COLUMN phone_number;

Key Takeaways

• ALTER TABLE allows schema evolution without rebuilding tables from scratch.

In Part 39, we analyze TRUNCATE vs DELETE!