Job-Ready SQL in an Afternoon - Unions

The video tutorial explains how to join tables vertically using SQL. It begins by discussing scenarios where vertical joins are necessary, such as when data is split across multiple tables. The tutorial then demonstrates creating subset tables using the CREATE TABLE statement and shows how to use the UNION statement to combine these tables vertically. It also covers extending the UNION operation to multiple tables and concludes with a discussion on cleaning up the database by dropping temporary tables.

What is the primary purpose of using a UNION statement in SQL?

• To update table records

• To delete duplicate rows

• To stack tables vertically

• To join tables horizontally

Why might data be split across multiple tables?

• To avoid using primary keys

• To reduce the size of individual tables

• To increase query complexity

• To make data retrieval slower

What SQL statement is used to create a new table from an existing table's data?

• CREATE TABLE

• UPDATE

• INSERT INTO

• DELETE

How does the UNION statement differ from a JOIN statement?

• JOIN stacks results vertically, UNION combines them horizontally

• JOIN is used for deleting records

• UNION is faster than JOIN

• UNION stacks results vertically, JOIN combines them horizontally

What happens when you use multiple UNION statements?

• It updates existing tables

• It deletes duplicate records

• It stacks multiple result sets vertically

• It creates a new table

What is the purpose of dropping temporary tables after using UNION?

• To increase database size

• To maintain a clean database environment

• To speed up queries

• To create new tables

Which SQL command is used to remove a table from the database?

• DELETE

• REMOVE

• DROP TABLE

• TRUNCATE