1. What is an Oracle database?
Hello! Welcome to Introduction to Oracle SQL. I am Sara, and later in this course you will meet my co-instructor Hadrien. Together we will teach you all about the fundamentals of Oracle SQL.
2. Learning SQL
Today, the world is in constant need of people who can work with huge amounts of data. Working with data stored in databases is a sought-after skill by many hiring employers.
3. Oracle SQL
A database is a set of data stored in a computer, usually structured in a way that makes the data easily accessible.
A relational database management system, or RDBMS, is a program that allows you to create, update, and administer a relational database. A relational database is based on the relational model of data, more on that later. Most RDBMSs use the SQL language to access the database.
Oracle Database is a popular RDBMS developed by Oracle.
PL/SQL, which stands for Procedural Language/SQL, or Oracle SQL, is Oracle's implementation of SQL.
4. Oracle SQL
The DB-Engines Ranking ranks database management systems according to their popularity. As you can see Oracle keeps hold at number one.
5. Oracle SQL
There are some advantages to using Oracle SQL. It is great for working with large databases, easy to use, has well-written documentation, and supports amazing new features.
The main disadvantage is that it is not free to use like its open source competitors and can be quite expensive.
6. Entity-Relationship Diagram (ERD)
Databases exist to support some existing real-world system.
Creating a good database design is very important. One tool that can help you model a real-world system is an Entity-Relationship Diagram, or ERD. An ERD is a graphical representation of the relationships among different entities.
7. Entity-Relationship Diagram (ERD)
The entities are the things that form the basis of the real-world system and are transformed into tables in a database. This example ERD shows six entities and the relationships between them.
A relationship between two entities signifies that they are associated with each other. For example, a track belongs to a certain album.
8. Entity-Relationship Diagram (ERD)
Once you have established the entities and their relationships, you can enhance your ERD by adding attributes to each entity. For example, for each customer you might want to track the customer’s first and last name as well as contact information such as their address.
9. Relational database
Now let’s start using the ERD to capture some actual data.
Consider this table, which shows a list of customers of a digital media store. The list has columns for Customer ID and attributes of the Customer entity. The reason you need a Customer ID is to make sure you have a unique identifier for each row in the list. The first row has a unique identifier of 1, the second row 2, and so on. These lists are what you will store in database tables.
10. Relational database
Recall the ERD from before. You just saw an example of the Customer table. In relational databases each entity will have its own table. Unique identifiers are used to connect data across multiple tables. We will cover this in more detail in chapter 3.
11. SQL
SQL is the industry-standard language that can be used to create databases, store data, change and analyze data, and get data back out.
12. Retrieving data
Let’s create a SQL command to display the contents of the Track table. You can use SELECT to identify the columns you want to retrieve. To indicate what table you want to look at, you can use FROM followed by the name of the table, Tracks. In this example, let's look at the track name, composer, and milliseconds.
Note that in Oracle SQL, a single statement is often spread over several lines to make it more readable. The code is not terminated with the physical end of a line.
When running this query, the following results are returned. Looks like there are some classic rock songs in the database!
13. Let's practice!
Your turn! Let's practice!