Creating databases and tables in Hadoop - Try It Yourself

Creating databases and tables

📖 Scenario: You are working with Hadoop's Hive to organize data for a small online bookstore. You want to create a database and tables to store information about books and authors.

🎯 Goal: Create a Hive database called bookstore. Then create two tables inside this database: authors and books. The authors table should have columns author_id (int) and author_name (string). The books table should have columns book_id (int), title (string), and author_id (int) to link to the authors.

📋 What You'll Learn

Create a Hive database named bookstore

Create a table named authors with columns author_id (int) and author_name (string)

Create a table named books with columns book_id (int), title (string), and author_id (int)

Use the bookstore database before creating tables

💡 Why This Matters

🌍 Real World

Organizing data in Hive databases and tables helps manage large datasets in big data projects like online bookstores.

💼 Career

Knowing how to create and manage Hive databases and tables is essential for data engineers and analysts working with Hadoop ecosystems.

1

Create the bookstore database

Write a Hive query to create a database called bookstore.

Hadoop

# Write the Hive query to create the database 'bookstore'
# Your code here

Hint

Use the CREATE DATABASE statement followed by the database name.

2

Select the bookstore database

Write a Hive query to use the database bookstore before creating tables.

Hadoop

CREATE DATABASE bookstore;
# Write the Hive query to use the database 'bookstore'
# Your code here

Hint

Use the USE statement to select the database.

3

Create the authors and books tables

Write Hive queries to create the authors table with columns author_id (int) and author_name (string), and the books table with columns book_id (int), title (string), and author_id (int).

Hadoop

CREATE DATABASE bookstore;
USE bookstore;
# Write the Hive query to create the 'authors' table
# Your code here

# Write the Hive query to create the 'books' table
# Your code here

Hint

Use CREATE TABLE with column names and types inside parentheses.

4

Display the tables in the bookstore database

Write a Hive query to show all tables in the bookstore database.

Hadoop

CREATE DATABASE bookstore;
USE bookstore;
CREATE TABLE authors (
  author_id INT,
  author_name STRING
);

CREATE TABLE books (
  book_id INT,
  title STRING,
  author_id INT
);
# Write the Hive query to show all tables in 'bookstore'
# Your code here

Hint

Use the SHOW TABLES; command to list tables in the current database.

Practice

1. What is the main purpose of creating a database in Hadoop?

easy

A. To run queries faster

B. To store data in rows and columns

C. To organize data into separate groups

D. To delete old data automatically

Solution

1. Step 1: Understand the role of a database

   A database is used to organize data logically into separate groups or collections.

2. Step 2: Differentiate database from tables

   Tables store data in rows and columns inside a database, but the database itself is for grouping.

3. Final Answer:

   To organize data into separate groups -> Option C

4. Quick Check:

   Database = Organize data groups [OK]

Hint: Databases group data; tables hold the data [OK]

Common Mistakes:

• Confusing database with table
• Thinking database stores data directly
• Assuming database speeds up queries automatically

2. Which of the following is the correct syntax to create a database named sales_db in Hive?

easy

A. CREATE DATABASE sales_db;

B. MAKE DATABASE sales_db;

C. CREATE DB sales_db;

D. NEW DATABASE sales_db;

Solution

1. Step 1: Recall Hive syntax for database creation

   The correct command to create a database in Hive is CREATE DATABASE database_name;.

2. Step 2: Check each option

   Only CREATE DATABASE sales_db; matches the correct syntax exactly.

3. Final Answer:

   CREATE DATABASE sales_db; -> Option A

4. Quick Check:

   CREATE DATABASE = correct syntax [OK]

Hint: Use CREATE DATABASE, not MAKE or NEW [OK]

Common Mistakes:

• Using MAKE or NEW instead of CREATE
• Abbreviating DATABASE as DB
• Missing semicolon at end

3. What will be the result of running this Hive query?

CREATE TABLE employees (id INT, name STRING, salary FLOAT);

medium

A. Creates a table named employees with three columns

B. Throws a syntax error due to missing database name

C. Creates a database named employees

D. Creates a table with no columns

Solution

1. Step 1: Analyze the CREATE TABLE statement

   The query uses correct syntax to create a table named employees with columns id, name, and salary.

2. Step 2: Check for errors or missing parts

   Database name is optional if default database is used; no syntax error here.

3. Final Answer:

   Creates a table named employees with three columns -> Option A

4. Quick Check:

   CREATE TABLE with columns = creates table [OK]

Hint: CREATE TABLE defines columns inside parentheses [OK]

Common Mistakes:

• Thinking database name is mandatory
• Confusing table and database creation
• Assuming syntax error without checking carefully

4. Identify the error in this Hive query:

CREATE TABLE users id INT, name STRING;

medium

A. Table name is invalid

B. Missing parentheses around column definitions

C. Data types are incorrect

D. CREATE TABLE keyword is misspelled

Solution

1. Step 1: Review the syntax for CREATE TABLE

   Column definitions must be enclosed in parentheses after the table name.

2. Step 2: Check the given query

   The query misses parentheses around id INT, name STRING, causing syntax error.

3. Final Answer:

   Missing parentheses around column definitions -> Option B

4. Quick Check:

   Columns need parentheses [OK]

Hint: Always use parentheses for columns in CREATE TABLE [OK]

Common Mistakes:

• Forgetting parentheses
• Assuming table name is wrong
• Thinking data types are invalid

5. You want to create a database company_db and inside it a table departments with columns dept_id INT and dept_name STRING. Which sequence of commands is correct?

hard

A. CREATE TABLE company_db.departments (dept_id INT, dept_name STRING);

B. CREATE DATABASE company_db; CREATE TABLE departments dept_id INT, dept_name STRING;

C. USE company_db; CREATE DATABASE company_db; CREATE TABLE departments (dept_id INT, dept_name STRING);

D. CREATE DATABASE company_db; USE company_db; CREATE TABLE departments (dept_id INT, dept_name STRING);

Solution

1. Step 1: Create the database first

   Use CREATE DATABASE company_db; to make the database.

2. Step 2: Switch to the new database

   Use USE company_db; to set the context for table creation.

3. Step 3: Create the table with correct syntax

   Use CREATE TABLE departments (dept_id INT, dept_name STRING); inside the database.

4. Final Answer:

   CREATE DATABASE company_db; USE company_db; CREATE TABLE departments (dept_id INT, dept_name STRING); -> Option D

5. Quick Check:

   Create DB, switch DB, then create table [OK]

Hint: Create DB, then USE it before creating tables [OK]

Common Mistakes:

• Trying to create table before database
• Wrong order of USE and CREATE DATABASE
• Missing parentheses in CREATE TABLE