The Best SQL Guide – An Ultimate guide for SQL Beginners
Structured Query Language, commonly known as SQL, is used to access and manipulate a database and is the standard language for database management systems, according to the ANSI. SQL statements can help retrieve or update data to a database.
Oracle, Ingres, Microsoft SQL Server, Sybase, etc. are some of the common database management systems that make use of SQL. Most of these have their own extensions, but common SQL commands like Select, Update, Insert, Create, etc. can be used to edit anything within a database.
SQL is considered as a fourth-generation language. It is not a language like C++ or JAVA, but it offers variables, logics, looping, etc. It is a standard language for manipulating, adding, or retrieving data from a database.
A brief history of SQL
In 1970, IBM researchers, Donald Chamberlin and Raymond Boyce developed the language SQL. Back then, it was known as SEQUEL and was created after Edgar Frank Todd released his paper, A Relational Model of Data for Large Shared Data Banks.
Todd said all the data in a database are related to each other, and Chamberlin and Boyce came up with SQL based on this. Malcolm Coxall wrote that the original version of SQL was used to manipulate data in IBM’s relational database management system, System R.
The SQL language was made available to the public after several years. Relational Software, which came to be known as Oracle, in 1979, released Oracle V2, which was its SQL version.
Now the International Standards Organization and American National Standards Institute have made SQL the standard language for relational databases. SQL vendors use the ANSI approved version of SQL as a base, but they all have their own modifications according to the needs.
To get a better understanding of the use of SQL, we need to be familiar with what a database is. Let us learn about a database first.
What is a Database?
A database is a storage system that allows users to access and manipulate the information inside of it. Tables are used in databases to store data and are identified by names and consist of multiple rows and columns.
A column has a name and information about the data type or attributes for the data inside it, while a row consists of the data for the columns. Most of the tables in a database and interlinked and have some or the other connection, and hence these are known as relational databases.
In recent times, there is a new thing among people who work with data and a whole new set of databases known as NoSQL. It is becoming popular and is a document based system. Still, many database systems use the traditional SQL language. NoSQL also has a query language, and it is based on SQL and is very similar to it.
How to use SQL?
Databases cannot understand languages like PHP, Ruby, Python, etc. and are configured to understand only SQL. Therefore, if you want to work in a field that involves databases, you need to work on your understanding of the SQL language.
Another thing that is unique to database management is tables. Tables have their own set of rows and columns and represent the data in a database. All the information you want on a database are stored in the form of tables.
Some basic SQL commands
The commands are used while writing the queries or statements that allow you to manipulate the data inside of a database. When you write these commands, the system interprets it and then processes the command. You will need complex commands to deal with more complex databases.
However, some familiar and frequently-used commands are there that even a beginner should be familiar with. The commands SELECT, FROM, and WHERE are the ones that are the most used, and other commands are just extensions of these.
Let us see an example of this query that will give us the name and ID of all the books written by Paulo Coelho.
SELECT bookid AS “id”, title
WHERE author = ‘Paulo Coelho’;
FROM is the command that links our query to the concerned table, where the data we are looking for is stored. It may be possible that the table already exists in the database, or you generated the table using the subqueries or joins.
WHERE acts as a filter to leave out the unwanted data and return back the exact information you need. It will not consider the rows that do not match with the value you put in the command.
SELECT Once we get the information we want from the tables, you need to express it and show it. This command is used to show the information we want to, and in the above example, we selected bookid and title. You can use the command AS to rename the columns too.
One more major area in basic SQL commands is the CRUD operations. You may know that CRUD stands for a database’s most basic operations which are Create, Read, Update, and Delete. All these four features are covered by the basic SQL commands: CREATE, INSERT, SELECT, UPDATE, DELETE.
CREATE TABLE table_name
Make sure you end all SQL statements with a , or ;. The names of the table and the columns should start with a letter and can be followed by numbers or underscores. However, the name must not exceed a total of 30 characters. Moreover, you cannot use SQL keywords for naming the table.
INSERT INTO table_name
(column_1, column_2, ……… , column_n)
VALUES (value_1, value_2, ……… , value_n)
This will help you insert a row of data to your table.
SET column_name = new_value
WHERE column_name = final_value;
This statement will update the columns of a table. The WHERE clause is essential so that the changes are made in the required columns else, the command will update each and every column of the table.
DELETE FROM table_name
WHERE column_name final value;
It is sometimes necessary to delete some unwanted data from the table, and the DELETE command helps us precisely with that. It is used to delete rows from a table. Here also, the WHERE clause will help specify the data you want to delete. Without this, all of the rows will be deleted.
Knowledge beyond the SQL Fundamentals
Apart from the basic SQL commands like creating a table and inserting and deleting data, it can be used for a lot more functions. It can control how the database behaves and give you special privileges of creating or deleting new databases or describe rows and columns within a database.
Different database systems have different SQL syntax, and you should go through the documentation once before you try out the advanced functions of a DBMS. However, before moving on to advanced and complex commands, make sure you are comfortable with the basics.
Areas in which SQL is used
If you work in the technology fields, where large amounts of data is used, then you surely must know about SQL. It is used in many major fields.
Music applications like Apple Music, Spotify, etc. use SQL to store a lot of music files by a number of artists. This data is operated to find what the user wants to listen to and store albums and preferences for the users.
Social media applications like Snapchat, Facebook, Instagram, etc. make use of SQL for data processing and store a user’s bio, photos, location, and other information. The database is updated with data when a user posts video or pictures or sends media or messages to friends. All this is stored in databases and can be retrieved if you want to view it again later.
Bank applications and payment portals make use of SQL to store and use data regarding transactions and information of users. These databases store confidential data and hence use high-level security in the SQL code to protect the data and keep it secure from a breach.
Some common SQL database systems
Database systems have a user interface and readymade templates and builders that a developer can work with. These tools are designed to make the work easier and efficient. There are many systems present today, so let’s take a look at some of the common Database systems.
Oracle is the world’s most used relational database system and gives you functionality for PDF storage, Cloud, Document storage, Graph DBMS, etc. It has made the relational model into an object-relational model that helps to store complex business models in the database. Its main characteristic is the independence of data storage from logical structures.
Even though Microsoft Access has got a bit old now, it still is in the top databases used for local storage. There is no access in centralized or remote storage, and it is used primarily for small and local databases.
MySQL is a popular database that is free to use and open source. In 2009, Oracle acquired it as a part of the Sun Microsystems acquisition. It is relatively easy to use and is fast and reliable. Its server generally works in embedded systems.
IBM DB2 is a database system that provides advanced analytics and data management for all warehouse and transactional workloads and is supported on Unix, Linux, and Windows OS. Its main features include storage optimization, continuous data availability, workload management, and advanced development tools. The latest version of it also has AI functionality for businesses.
PostgreSQL is an open source, powerful relational database system that combines the SQL language with multiple features designed to store and manipulate complicated data workloads. It is written in the C language. Its main features include its reliability, top-level features, data integrity, architecture, and extensibility that deliver innovative and effective solutions.
Where can you learn the SQL language?
If you are planning to work in a field that involves data interpretation and management, you need to be good with your SQL skills. If you are just beginning, no need to worry as there are many ways where you can start learning SQL.
Pluralsight’s SQL Classes Bundle Online
Codecademy’s Learn SQL Online
Codecademy’s SQL course will help you learn and work on relational databases using SQL. Practice with four projects on how to build queries and work with data in more than one table. Learn basic keywords first and then go on to complex queries.
Udemy’s The Complete SQL Bootcamp
It is a great course for beginners that does not require any previous experience in the field. It comes with PgAdmin that helps to work with PostgreSQL database. The concepts taught in this course apply to all major databases like MySQL, Oracle, etc.
A good book on SQL will cover all the fundamentals and basics in depth. It will give you all the knowledge you need to know. Moreover, you will get familiar with the common mistakes that coders make while writing code, and you can avoid them.
Some good books to start learning SQL are
Sams Teach Yourself SQL in 10 Minutes
Learning SQL by Alan Beaulieu
The Art of SQL by Peter Robson
You can learn and read as much as you want, but the best way to learn SQL is actually practicing it yourself. Install a free database and begin writing and running your own queries on data. Practice makes you perfect. It will be easy to get familiar with the basics of SQL, and slowly you can move on to more advanced and complicated things.
SQL is a very in-demand skill currently, and almost all the top companies use it for their databases. The above guide tells you all that you need to know about the SQL language and even how to use its basics.
If you are ready to take the next step, get started with learning SQL. The guide has all the resources to guide you on the right path. Work on your skills, and then slowly, step-by-step, you will get a grip over the SQL language.