Introduction to Relational Databases in SQL

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Course Description

You’ve already used SQL to query data from databases. But did you know that there's a lot more you can do with databases? You can model different phenomena in your data, as well as the relationships between them. This gives your data structure and consistency, which results in better data quality. In this course, you'll experience this firsthand by working with a real-life dataset that was used to investigate questionable university affiliations. Column by column, table by table, you'll get to unlock and admire the full potential of databases. You'll learn how to create tables and specify their relationships, as well as how to enforce data integrity. You'll also discover other unique features of database systems, such as constraints.

Introduction to Relational Databases in SQL

In this chapter, you'll create your very first database with a set of simple SQL commands. Next, you'll migrate data from existing flat tables into that database. You'll also learn how meta-information about a database can be queried.

Now let’s get into the best practices of database engineering. It's time to add primary and foreign keys to the tables. These are two of the most important concepts in databases, and are the building blocks you’ll use to establish relationships between tables.

After building a simple database, it's now time to make use of the features. You'll specify data types in columns, enforce column uniqueness, and disallow NULL values in this chapter.

In the final chapter, you'll leverage foreign keys to connect tables and establish relationships that will greatly benefit your data quality. And you'll run ad hoc analyses on your new database.

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Your first database
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In this chapter, you'll create your very first database with a set of simple SQL commands. Next, you'll migrate data from existing flat tables into that database. You'll also learn how meta-information about a database can be queried.
View Chapter Details Play Chapter Now
Enforce data consistency with attribute constraints

After building a simple database, it's now time to make use of the features. You'll specify data types in columns, enforce column uniqueness, and disallow NULL values in this chapter.
View Chapter Details Play Chapter Now
Uniquely identify records with key constraints

Now let’s get into the best practices of database engineering. It's time to add primary and foreign keys to the tables. These are two of the most important concepts in databases, and are the building blocks you’ll use to establish relationships between tables.
View Chapter Details Play Chapter Now
Glue together tables with foreign keys

In the final chapter, you'll leverage foreign keys to connect tables and establish relationships that will greatly benefit your data quality. And you'll run ad hoc analyses on your new database.
View Chapter Details Play Chapter Now

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Timo Grossenbacher

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Timo Grossenbacher is a project lead for automated journalism at Swiss publisher Tamedia. Prior to that, he used to be a data journalist working with the Swiss Public Broadcast (SRF), where he used scripting and databases for almost every data-driven story he published. He also teaches data journalism at the University of Zurich and is the creator of rddj.info – resources for doing data journalism with R. Follow him at grssnbchr on Twitter or visit his personal website.

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Introduction to Relational Databases in SQL

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Loved by learners at thousands of top companies:

Course Description

Your first database

Introduction to relational databases

Attributes of relational databases

Query information_schema with SELECT

Tables: At the core of every database

CREATE your first few TABLEs

ADD a COLUMN with ALTER TABLE

Update your database as the structure changes

RENAME and DROP COLUMNs in affiliations

Migrate data with INSERT INTO SELECT DISTINCT

Delete tables with DROP TABLE

Uniquely identify records with key constraints

Keys and superkeys

Get to know SELECT COUNT DISTINCT

Identify keys with SELECT COUNT DISTINCT

Primary keys

Identify the primary key

ADD key CONSTRAINTs to the tables

Surrogate keys

Add a SERIAL surrogate key

CONCATenate columns to a surrogate key

Test your knowledge before advancing

Enforce data consistency with attribute constraints

Better data quality with constraints

Types of database constraints

Conforming with data types

Type CASTs

Working with data types

Change types with ALTER COLUMN

Convert types USING a function

The not-null and unique constraints

Disallow NULL values with SET NOT NULL

What happens if you try to enter NULLs?

Make your columns UNIQUE with ADD CONSTRAINT

Glue together tables with foreign keys

Model 1:N relationships with foreign keys

REFERENCE a table with a FOREIGN KEY

Explore foreign key constraints

JOIN tables linked by a foreign key

Model more complex relationships

Add foreign keys to the "affiliations" table

Populate the "professor_id" column

Drop "firstname" and "lastname"

Referential integrity

Referential integrity violations

Change the referential integrity behavior of a key

Roundup

Count affiliations per university

Join all the tables together