DROP TABLE and ALTER TABLE in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SQL command DROP TABLE do?

The DROP TABLE command deletes an entire table and all its data permanently from the database.

beginner

How do you add a new column to an existing table in SQL?

Use ALTER TABLE table_name ADD column_name datatype; to add a new column to a table.

intermediate

What happens if you try to DROP TABLE a table that does not exist?

You get an error unless you use DROP TABLE IF EXISTS table_name; which avoids the error if the table is missing.

intermediate

How can you rename a table using SQL?

Use ALTER TABLE old_table_name RENAME TO new_table_name; to rename a table.

intermediate

Can you remove a column from a table using ALTER TABLE? How?

Yes, use ALTER TABLE table_name DROP COLUMN column_name; to remove a column from a table.

What does DROP TABLE employees; do?

A Deletes the employees table and all its data

B Deletes only the data inside employees table

C Renames the employees table

D Adds a new column to employees table

DROP TABLE removes the entire table and its data permanently.

Which SQL command adds a new column named age to a table users?

A DROP TABLE users ADD age;

B ALTER TABLE users DROP COLUMN age;

C ALTER TABLE users ADD age INT;

D CREATE COLUMN age ON users;

ALTER TABLE users ADD age INT; adds a new column called age of type integer.

How do you rename a table old_name to new_name?

A ALTER TABLE old_name RENAME TO new_name;

B DROP TABLE old_name RENAME TO new_name;

C RENAME TABLE old_name TO new_name;

D ALTER TABLE old_name CHANGE TO new_name;

The correct syntax to rename a table is ALTER TABLE old_name RENAME TO new_name;.

What happens if you run DROP TABLE IF EXISTS my_table; and my_table does not exist?

A Table is renamed

B Error occurs because table is missing

C Table is created

D No error, command runs safely

IF EXISTS prevents errors if the table does not exist.

Which command removes a column named address from the customers table?

A DROP TABLE customers.address;

B ALTER TABLE customers DROP COLUMN address;

C ALTER TABLE customers REMOVE address;

D DELETE COLUMN address FROM customers;

Use ALTER TABLE customers DROP COLUMN address; to remove a column.

Explain what the DROP TABLE command does and when you might use it.

Think about removing a whole spreadsheet from your files.

Describe how to use ALTER TABLE to change a table structure, including adding and removing columns.

Imagine changing the columns in a spreadsheet without losing the data.