What Is SQL? Definition, Elements, Examples, and Uses in 2022

Structured Query Language (SQL) is defined as a standard programming language utilized to extract, organize, manage, and manipulate data stored in relational databases. This article explains the fundamentals of the SQL programming language, its elements, examples, and uses in 2022.

What Is SQL?
Elements of SQL
Examples of SQL
Uses of SQL in 2022

What Is SQL?

Structured Query Language (SQL) refers to a standard programming language utilized to extract, organize, manage, and manipulate data stored in relational databases. SQL is thereby referred to as a database language that can execute activities on databases that consist of tables made up of rows and columns.

SQL plays a crucial role in retrieving relevant data from databases, which can later be used by various platforms such as Python or R for analysis purposes. SQL can manage several data transactions simultaneously where large volumes of data are written concurrently.Â

SQL is an American National Standards Institute (ANSI) standard that operates via multiple versions and frameworks to handle backend data across various web applications supported by relational databases such as MySQL, SQL Server, Oracle PostgreSQL, and others.

Top companies owned by Meta Inc., such as Facebook, WhatsApp, and Instagram, all rely on SQL for data processing and backend storage.

How does SQL work?

As an SQL query is written and run, it is processed by the â€˜query language processor’ having a parser and query optimizer. The SQL server then compiles the processed query in three stages:

1. Parsing: This refers to a process that cross-checks the syntax of the query.

2. Binding: This step involves verifying query semantics before executing it.

3. Optimization: The final step generates the query execution plan. The objective here is to identify an efficient query execution plan that runs in minimal time. This implies that the shorter the response time for the SQL query, the better the results. Several combinations of plans are generated to have a practical end execution plan.

Essential SQL benefits

SQL offers several benefits as it is a user-friendly language accessible across platforms.Â

Let’s understand the key benefits of SQL:

Portable language: SQL, being a portable language, can be transferred from one device to another, where the devices can range from personal computers and servers to laptops and even some mobile devices. The language is capable of running on local internet and intranet systems.
Fast query processing: Irrespective of the volume of data, SQL is capable of inserting, deleting, retrieving, and manipulating data quickly and efficiently while ensuring data accuracy. This enables fast data sharing between users.Â
No coding skills required: SQL does not demand coding skills like other programming languages. Its user-friendly trait makes it accessible to all users as they can manage SQL with the help of keywords such as â€˜create,’ â€˜insert,’ â€˜select,’ â€˜update,’ and others without possessing any programming skills.
Uniform platform with standardized language: SQL uses English as a standard language; hence, it is easy for all users to understand, learn, write, and interpret without much difficulty. The English words and statements make SLQ accessible to everyone, including people with little or no previous experience.
Offers multiple data views: SQL provides a facility to create multiple data views, where different users can visualize the database structure and its content differently.
Open source code. Open source SQL solutions such as MySQL, MariaDB, and PostGresSQL provide accessible SQL databases. This attracts the participation of larger communities at a lower cost.
Top database management system (DBMS) vendors use SQL: The DBMS systems of top companies such as IBM, Oracle, and Microsoft use SQL, considering the comprehensive benefits it offers.
Interactive language: SQL is an interactive and interpretive language. As such, it reduces the chances of miscommunication or misunderstanding between users.

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Elements of SQL

SQL is the go-to-choice of most database users due to its easy usability and how the queries can carry out varied functions on vast amounts of structured data.

SQL programming language has the following vital elements:

1. Keywords

2. Clauses

3. Expressions

4. Predicates

5. Queries

Let’s understand the role of each element in SQL programming:

1. Keywords: Keywords refer to a set of words that allow you to perform operations on your database. Consider the example of the keyword â€˜LIKEâ€˜; it searches for a specific data pattern in the database.

For example, let’s say we need to identify the names of families living in the Boston area who have â€˜Luis’ as their last name. The following SQL query will fetch the relevant results for this problem statement:

SELECT * FROM [BOSTON] WHERE NAME LIKE â€˜%LUIS’

Similarly, different keywords perform various operations on the databases. The following are some examples of such keywords with their functional roles:

CREATE: This keyword helps in creating a database structure or simply tables, views, and an index
INSERT: It adds data to the rows of a table
SELECT: Selects data from database or table
FROM: Indicates the table from which data needs to be fetched
WHERE: It filters the data so that only relevant data matching certain conditions is fetched
UPDATE: Updates existing rows in a table
DELETE: It deletes the existing rows in a table

2. Clauses: Clauses refer to the in-built functions that filter out data and retrieve the required data from the database or table. It is suitable when handling large databases. Clauses are a part of the SQL statement.

Let’s consider a use case where you need to select age, email, and address from the database. One would then represent the clause as â€˜SELECT Age, Email, and Address,’ where SELECT is a keyword and age, email, and address reveal certain information to run the SQL query and retrieve the required data.

3. Expressions: SQL expressions represent a formula typically written in a query format. It combines one or more values, operators, and SQL functions that evaluate a specific value. Moreover, SQL expressions are broadly divided into three types, namely, Boolean, numeric, and date.

Let’s consider an example of the Boolean expression that fetches data by matching single values. If you want to identify employees whose salaries are equal to 5,000, one can use the following SQL query:Â

SELECT * FROM EMPLOYEES WHERE SALARY = 5000;

4. Predicates: Predicates refer to keywords that reveal a relationship between two expressions and result in a true or false value. It is just another term for an expression that is used to determine an unknown or TRUE/FALSE condition.

For example, consider the following SQL statement:Â

SELECT * FROM CUSTOMERS WHERE Product = â€˜Television’;Â

Here, â€˜Product = Television’ is the predicate of the SQL statement.

5. Queries: SQL queries refer to statements used to request or retrieve data from a database. For example, let’s say you want to retrieve the first name and customer number of all customers whose last name is â€˜Lobo’. The following query will fetch the relevant data from the database:

SELECT First_Name, Customer_No FROM Customers WHERE Last_Name=’Lobo’;

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Examples of SQL

SQL queries a relational database to retrieve data that is represented in a table format (rows and columns). Here, the rows symbolize different objects, while the columns symbolize the attributes of those objects.

Let’s understand some basic examples of SQL programming language.

1. Let’s create a table that stores weather data for different cities and has no duplicate ID fields.

CREATE TABLE WEATHER

(ID INTEGER PRIMARY KEY,

CITY_US CHAR (30),

STATE_US CHAR(30),

LATITUDE_N REAL,

LONGITUDE_W REAL);

Now that the table is created at the backend, let’s populate the table WEATHER with data:

INSERT INTO WEATHER VALUES (19, â€˜Los Angeles,’ â€˜CA,’ 34, 118);

INSERT INTO WEATHER VALUES (38, Detroit, â€˜MI,’ 42, 83);

INSERT INTO WEATHER VALUES (97, Spokane, â€˜WA,’ 47, 117);

2. Upon populating the table, you can view the table WEATHER with the following SQL query in an undefined order:

SELECT * FROM WEATHER;

ID	CITY_US	STATE_US	LATITUDE_N	LONGITUDE_W
19	Los Angeles	CA	34	118
38	Detroit	MI	42	83
97	Spokane	WA	47	117

3. To view cities and states whose latitude > 40, use the following query:

SELECT * FROM WEATHER WHERE LATITUDE_N > 40;

ID	CITY_US	STATE_US	LATITUDE_N	LONGITUDE_W
38	Detroit	MI	42	83
97	Spokane	WA	47	117

Such a selection of rows is the fundamental way of imposing â€˜restriction’ on the data to be viewed.

4. Let’s look at an example that allows you to select only certain columns from the original table, such as ID, CITY_US, and LATITUDE_N columns:

SELECT ID, CITY_US, LATITUDE_N FROM WEATHER;

ID	CITY_US	LATITUDE_N
19	Los Angeles	34
38	Detroit	42
97	Spokane	47

Such a selection of specific columns is referred to as â€˜projection’ in SQL terminology.

5. Now let’s combine the â€˜restrict’ and â€˜project’ use cases in a single SQL query:

SELECT ID, CITY_US, STATE_US FROM WEATHER WHERE LATITUDE_N > 40;

ID	CITY_US	STATE_US
38	Detroit	MI
97	Spokane	WA

These are some of the interactive SQL examples that one can use to fiddle with the relational database model.

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Uses of SQL in 2022

SQL is a popular domain-specific language used for transacting with databases. It can perform several operations on databases or tables, such as extracting, modifying, and storing data, among many others.

Let’s now understand some of the critical uses of SQL in 2022:

1. Management of relational databases

The history of relational databases dates back to 1969 when scientist Edgar F. Codd first defined it. Then, in 1970, software was developed to maintain a relational model using SQL language. This code was referred to as the Relational Database Management System (RDBMS). In relational databases, data is stored in rows. These are termed â€˜tuples’ and are grouped based on common relations.

Thus, the very fundamental use of SQL is to maintain data in RDBMS and perform operations on them by using SQL queries.

2. Performing basic database operations

SQL uses several key commands while interacting with databases. These include:Â

Data Definition Language (DDL): SQL uses commands to create and maintain databases such as CREATE, DROP, ALTER, TRUNCATE, and COMMENT.
Data Query Language (DQL): This refers to SQL commands used to retrieve data from databases. The commonly used SQL command here is SELECT.
Data Manipulation Language (DML): These refer to SQL commands used to manipulate data and perform critical operations on databases, such as INSERT, UPDATE, and DELETE.
Data Control Language (DCL): These refer to SQL control commands that grant users permission or access to perform certain operations. For example, REVOKE is the control command that revokes the access permission given to users.

3. Allowing database transaction control

SQL is used to maintain consistency in database transactions. It follows basic ACID rules, where ACID refers to atomicity, consistency, isolation, and durability. Transaction processing is done when it obeys all these fundamental properties.

Atomicity implies that every transaction is an atomic unit, and all instructions occur successfully, or none of them execute at all. Consistency means that a database should be consistent before and after every transaction. Isolation implies that several transactions running concurrently should not affect each other by any means. Lastly, durability suggests that in the event of a software or system failure, changes made to the data should persist post transaction completion.

Some common control commands include COMMIT and ROLLBACK.

4. Execution of SQL UNION and JOIN commands

SQL uses UNION and JOIN commands to merge two tables in a database to provide a single result or output. Let’s consider a scenario where you want to view the information of a customer who bought certain products from a mall. The customer details exist in the â€˜customer’ table, while the product details are in the â€˜product’ table. Hence, to view customer information about who bought a specific product, one can perform a JOIN operation.

JOIN is further divided into four types:

INNER JOIN
LEFT (OUTER) JOIN
RIGHT (OUTER) JOIN
FULL (OUTER) JOIN

All these JOIN operations are represented as in the following figure:

5. SQL for websites

Every website has a backend database that contains tons of data (users, products, etc.) which needs to be retrieved as and when required. Today, most interactive websites tend to use SQL query language to extract and store data in the database. For example, ecommerce sites such as Amazon and Flipkart use MySQL for data management that supports standard SQL. Moreover, movie and accommodation booking sites also rely on query language to perform operations on the data as needed.

6. Compatibility and library support

Companies such as Amazon, Google, Microsoft, Oracle, and others use relational databases such as Microsoft SQL Server, MS Access, Oracle database, MYSQL, etc. SQL is typically compatible with most such relational databases.

Moreover, SQL offers a collection of libraries, such as SQLite, which help connect client web apps to database developers. Such library support of SQL allows users to work with clients’ datasets.

7. Integration with other scripting languages

SQL integrates with popular scripting languages such as Python and R. This allows SQL to manage databases that are supported by these languages, and it is most helpful for users such as data analysts, data scientists, ML engineers, etc., who tend to handle vast amounts of data simultaneously.

SQL is a functional query language as it uses simple queries to manage large datasets. Moreover, complex operations such as data filtering, slicing, indexing, etc., can be nailed by using simple clauses such as WHERE and others with logical operators and conditions in the SQL queries

8. SQL for machine learning

Machine learning comes into the picture when you intend to handle a humongous amount of data. Also, wherever large data sets exist, SQL inevitably finds its place in such situations.

Google’s cloud platform BigQuery is an excellent example of SQL for ML. The platform uses SQL queries and tools to create and execute various ML models. In simple words, ML models are invoked on structured data by using SQL. Hence, SQL’s ML support and its easy integration with scripting languages make it a suitable query language for applications that handle vast volumes of data.

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Takeaway

Databases built on relational models are relational databases that use tables to store data. SQL is a widely known programming language that helps retrieve and manipulate data residing in such relational databases. Some fundamental components often used in an SQL query include SELECT, FROM, and WHERE, along with some clauses and functions depending on the intended database operations.

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