Introduction
Welcome to the captivating world of SQL databases! In today's data-driven landscape, mastering SQL (Structured Query Language) and its dynamic interaction with databases is not just valuable—it's essential. Whether you're a burgeoning data enthusiast eager to explore, a software developer poised for innovation, or a seasoned professional seeking to expand your skill set, this guide is your gateway to unlocking the potential of SQL databases. Join us on a journey through the fundamentals, from demystifying what SQL databases are to empowering you with the tools to wield them effectively.
What is a Databases?
SQL database or relational database is a collection of highly structured tables, wherein each row reflects a data entity, and every column defines a specific information field. Relational databases are built using the structured query language (SQL) to create, store, update, and retrieve data.
SQL or Relational databases are used to store and manage the data objects that are related to one another, i.e. the process of handling data in a relational database is done based on a relational model.
This relational model is an approach to manage data in a structured way (using tables). A system used to manage these relational databases is known as Relational Database Management System (RDBMS). (We'll delve deeper into relational databases in our upcoming articles, exploring their intricacies and practical applications.)
Differences between NoSQL & Relational database
Relational Database Management Systems (RDBMS) and NoSQL databases are two broad categories of database management systems, each with its own characteristics:
| Feature | NoSQL Database | Relational Database |
| Query Language | Supports a very simple query language. | Supports a powerful query language. |
| Schema | Has no fixed schema. | Has a fixed schema. |
| Consistency | Only eventually consistent. | Follows ACID properties. (Atomicity, Consistency, Isolation, Durability) |
| Transactions | Doesn't support transactions (only simple transactions). | Supports transactions (including complex transactions with joins). |
| Data Velocity | Used to handle data coming in high velocity. | Used to handle data coming in low velocity. |
| Data Source | Data arrive from many locations. | Data arrive from one or few locations. |
| Data Type | Can manage structured, unstructured, and semi-structured data. | Manages only structured data. |
| Failure Point | Has no single point of failure. | Has a single point of failure with failover. |
| Data Volume | Can handle big data or data in a very high volume. | Used to handle moderate volume of data. |
| Structure | Has a decentralized structure. | Has a centralized structure. |
SQL Database Table Structure
In SQL database servers, data is organized into tables. Tables are essential database objects used to collect and organize data in a structured manner, utilizing rows and columns.
What is a Table?
A table in a relational database management system (RDBMS) is a container for related data entries. It comprises multiple rows and columns, where each row represents a unique data entry, and each column represents a specific attribute of the data.
Tables are the primary and simplest form of data storage in a relational database. Let's consider an example of a table named CUSTOMERS, which stores information such as customer ID, name, age, salary, city, and country.
| ID | Name | Age | Salary | City | Country |
| 1 | Ramesh | 32 | 2000.00 | Maryland | USA |
| 2 | Mukesh | 40 | 5000.00 | New York | USA |
| 3 | Sumit | 45 | 4500.00 | Muscat | Oman |
| 4 | Kaushik | 25 | 2500.00 | Kolkata | India |
What is a Record or a Row?
A record is also called as a row of data is each individual entry that exists in a table. For example, there are 7 records in the above CUSTOMERS table.
Following is a single row of data or record in the CUSTOMERS table − A record is a horizontal entity in a table.
| ID | Name | Age | Salary | City | Country |
| 1 | Ramesh | 32 | 2000.00 | Hyderabad | India |
What is a Column*?*
A column is a vertical entity in a table that contains all information associated with a specific field in a table. For example, our CUSTOMERS table has different columns to represent ID, Name, Age, Salary, City and Country.
ID: Represents the unique identifier for each customer.
Name: Holds the name of each customer.
Age: Stores the age of each customer.
Salary: Contains the salary information of each customer.
City: Represents the city where each customer resides.
Country: Stores the country of each customer.
Keys and Constraints:
Primary Key: A primary key is a unique identifier for each row in a table. It ensures the uniqueness and integrity of the data.
Foreign Key: A foreign key is a column or set of columns that establishes a relationship between two tables. It references the primary key of another table.
Constraints: Constraints are rules defined on columns to enforce data integrity and maintain consistency. Common constraints include NOT NULL, UNIQUE, CHECK, and DEFAULT.
Conclusion
In conclusion, this guide has provided you with a solid introduction to SQL databases, covering essential concepts such as SQL, databases, the difference between RDBMS and NoSQL, and key database components like tables, rows, columns, and keys.
Understanding SQL and databases is fundamental in today's data-driven world, whether you're a student, a professional developer, or someone interested in exploring the vast field of data management. With this foundation, you're well-equipped to embark on your journey to becoming proficient in database management and development.
In our upcoming blogs, we'll delve deeper into the world of SQL databases, focusing specifically on keys and constraints. We'll explore how keys ensure data integrity and facilitate relationships between tables, and we'll discuss various types of constraints that enforce rules and maintain consistency in your database.
Stay Connected
Stay tune for more insightful discussions and Feel free to share your thoughts in the comments! We're also eager to hear what topics you'd like us to cover in our upcoming articles.
Until then, keep exploring, practicing, and expanding your knowledge. The world of databases awaits your exploration!