SQL is a Structured query language used to access and manipulate data in databases. SQL stands for Structured Query Language. We can create, update, delete, and retrieve data in databases like MySQL, Oracle, PostgreSQL, etc. Overall, SQL is a query language that communicates with databases.
In this SQL tutorial, you’ll learn all the basic to advanced SQL concepts like SQL queries, SQL join, SQL injection, SQL insert, and creating tables in SQL.
SQL Uses
SQL's integration with various technologies makes it essential for managing and querying data in databases. Whether it's in traditional relational databases (RDBMS) or modern technologies such as machine learning, AI, and blockchain, SQL plays a key role. It works seamlessly with DBMS (Database Management Systems) to help users interact with data, whether stored in structured RDBMS or other types of databases.
- Data Science & Analytics: Used for querying large datasets, data cleaning, and analysis. Analysts use SQL to generate reports and insights that inform business decisions.
- Machine Learning & AI: Helps in preparing and managing the data required for training machine learning models and AI algorithms. It is used for data cleaning, transformation, and extraction.
- Web Development: Used to manage user data, e-commerce transactions, and content management in websites and applications built with frameworks like Django, Node.js, and Ruby on Rails.
- Cloud and Big Data: SQL is integrated into cloud-based databases (e.g., Amazon RDS, Microsoft Azure SQL) and Big Data platforms (e.g., Apache Hive) to enable seamless data querying and management.
- Blockchain and Decentralized Systems: In blockchain systems, SQL can be used to manage off-chain data, providing efficient data storage and retrieval alongside decentralized ledger technology.
How SQL work?
When you interact with a database, you typically use SQL commands to perform these operations. These commands are translated into actions by the SQL Engine, the core component responsible for processing queries. The SQL Engine parses and compiles SQL queries, optimizing and executing them to interact with the stored data. The SQL Engine also ensures that data retrieval and modifications are efficient and consistent.
Different DBMS tools (like MySQL, SQL Server, etc.) provide an interface and APIs that users can use to interact with the database. These tools provide a user-friendly way to write and execute SQL queries, but internally, they rely on their respective SQL Engines to process these commands.
For example, MySQL uses its own SQL Engine to parse, optimize, and execute queries, while SQL Server has a different SQL Engine for the same task. These engines ensure that SQL queries are executed in a way that respects the underlying database structure and the specific DBMS’s optimizations.
Example
In this detailed SQL tutorial for beginners, we'll explore practical SQL examples for managing employee data within a database. We'll create a table to store employee information and populate it with sample data like Employee_Id, Name, Age, Department, and Salary.
If you want to retrieves data from the employees table where the salary is greater than 55000.00 then we will use SELECT Statement.
Query:
SELECT * FROM employees WHERE Salary > 55000.00;
Basics
SQL or Structured Query Language is a fundamental skill for anyone who wants to interact with databases. This standard Query Language all users to create, manage, and retrieve data from relational databases. In this SQL tutorial PDF, we have listed all the basics of SQL. Explore this section to sharpen your SQL basics.
Create Database
The first step to storing the information electronically using SQL includes creating database. And in this section we will learn how to Create, Select, Drop, and Rename databases with examples.
Tables
The cornerstone of any SQL database is the table. Basically, these structure functions is very similar to spreadsheets, which store data in very organized grid format. In this section, you will learn how to Create, Drop, Delete, and more related to Table.
CRUD Operations
In this section, you will learn about the SQL Queries like SELECT statement, SELECT LAST, and more. Explore this section and learn how to use these queries.
Clauses
Unlock the power of SQL Clauses with this SQL tutorial. Here in this section, you will learn how to use SELECT, WHERE, JOIN, GROUP BY, and more to query databases effectively.
Operators
SQL Operators" refers to the fundamental symbols and keywords within the SQL that enable users to perform various operations and SQL AND, OR, LIKE, NOT, and more operators on databases. Here, we have discussed all the SQL operators in a detailed manner with examples.
Aggregate Functions
Whether you are calculating the total sales revenue for a particular product, finding the average age of customers, or determining the highest value in a dataset, SQL Aggregate Functions make these tasks straightforward and manageable.
Data Constraints
Constraints act as rules or conditions imposed on the data, dictating what values are permissible and what actions can be taken. They play a crucial role in maintaining the quality and coherence of the database by preventing errors. So, explore this section to get a hand on SQL Data Constraints.
Joining Data
SQL joins serve as the weaver's tool, allowing you to seamlessly merge data from multiple tables based on common threads. So explore this section to learn how to use JOIN command.
Functions
SQL functions offer an efficient and versatile approach to data analysis. By leveraging these functions within your queries, you can enhance the depth and accuracy of your insights, transforming raw data into actionable knowledge.
Views
Views makes easier for anyone to access the information they need, without getting bogged down in complicated queries. Views also act like a helpful security guard, keeping the most sensitive information in the back room, while still allowing access to what's needed.
Indexes
Indexes work by organizing specific columns in a particular order, allowing the database to quickly pinpoint the information you need. And in this section, we have listed all the points that one has to learn while learning SQL.
Subquery
Subqueries allow you to perform nested queries within a larger query, enabling more complex data retrieval. They help in filtering data or performing operations on data that would otherwise require multiple queries.
Miscellaneous Topics
In this miscellaneous section, you will encounter concepts like stored procedures for automating repetitive tasks, triggers for automated actions based on data changes, and window functions for complex calculations within a single query.
Exercises, Interview Questions & Cheat Sheet
This section provides hands-on exercises and commonly asked interview questions to help solidify your SQL knowledge. It also includes a cheat sheet for quick reference, making SQL concepts easier to grasp.
Advanced SQL & Databases
Advanced SQL topics explore techniques like optimization, complex joins, and working with large-scale databases. This section also covers the use of advanced functions and stored procedures to handle sophisticated database operations.
Database Design and Modeling
Database design focuses on creating an efficient database structure that is scalable and meets user requirements. Modeling involves defining relationships, entities, and constraints to ensure data integrity and efficient querying.
Database Security
Database security protects data from unauthorized access, corruption, and breaches. It includes encryption, authentication, and user privilege management to safeguard sensitive information stored in databases.
Projects
SQL projects provide practical experience in applying SQL concepts to real-world problems. These projects allow you to build and manage databases for various domains, enhancing your hands-on skills in database design and querying.
Database Connectivity
Database connectivity enables applications to interact with databases through established protocols and drivers. This section covers how to establish secure connections and manage database interactions in programming languages like PHP, Python, and Java.
Applications
In data-driven industries where managing databases is very important in regular, Here are some important SQL applications.
- To support client/server architecture, software engineers use SQL to establish the connection between the back-end and front-end.
- SQL can also be used in the 3-tier architecture of a client, an application server, and a database.
- SQL is used as a Data Definition Language(DDL) in which we can independently create a database, define the structure, use it, and discard it when its work is done.
- SQL is used as a Data Manipulation Language(DML) in which we can enter data, modify data, and extract data.
- SQL is used as a Data Control Language(DCL) it specifies how we can protect our database against corruption and misuse.
SQL TutorialJobs and Opportunities
There are numerous companies around the globe seeking SQL professionals, and they pay high packages. The average salary of SQL developers is around 40,000–65,000 INR. In this section, we have listed some of the top giant companies that hire SQL experts.
Advantages
SQL or Structured Query Language, is one of the most popular query languages in the field of data science. SQL is the perfect query language that allows data professionals and developers to communicate with their databases.
In the below section, we have listed some of the most prominent advantages or benefits of Structured Query Language:
- Simple and Easy to Learn: Most of the commands and syntax in SQL are like normal English, which makes SQL easy to learn. Along with this, SQL follows a logical structure that helps promote readability and understanding.
- Efficiency and Speed Execution: Well, SQL is optimized for RDBMS, which means relational database, and this thing ensures fast query execution.
- Standardization: SQL is a widely accepted standard query language and ensures compatibility across different database systems.
- Scalable: SQL can efficiently manage massive datasets, accommodating growth without compromising performance.
Latest Trends and Updates
The world of SQL is constantly evolving, so here are some of the hottest trends and updates to keep you in the loop:
Big Data and SQL: Big data store vast amounts of information from various sources. SQL queries act as a bridge, enabling users to extract specific data subsets for further analysis.
Cloud Computing and SQL: Cloud SQL lets your database scale up or down based on your needs. Along with that it very cost effective so you have only pay for the resources you use, making it a cost-efficient option for businesses of all sizes.
Machine Learning and SQL: Data scientists leverage SQL to prepare and clean data for analysis, making it a crucial skill for this field.
Real-time Data Processing with SQL: The need for immediate insights is driving the growth of streaming SQL. This allows you to analyze data as it's generated, providing real-time visibility into what's happening.
SQL in Data Governance and Compliance: With stricter data privacy regulations, SQL is playing a role in ensuring data security and compliance. Queries can be used to control access to sensitive information and track data usage for auditing purposes.
Quick Links:
Similar Reads
SQL Tutorial
SQL is a Structured query language used to access and manipulate data in databases. SQL stands for Structured Query Language. We can create, update, delete, and retrieve data in databases like MySQL, Oracle, PostgreSQL, etc. Overall, SQL is a query language that communicates with databases. In this
11 min read
SQL Basics
What is Database?
In today’s data-driven world, databases are indispensable for managing, storing, and retrieving information efficiently. From small-scale businesses to global enterprises, databases serve as the backbone of operations, powering applications, websites, and analytics systems. In this comprehensive art
15 min read
Types of Databases
Databases are essential for storing and managing data in today’s digital world. They serve as the backbone of various applications, from simple personal projects to complex enterprise systems. Understanding the different types of databases is crucial for choosing the right one based on specific requ
11 min read
Introduction of DBMS (Database Management System)
A Database Management System (DBMS) is a software solution designed to efficiently manage, organize, and retrieve data in a structured manner. It serves as a critical component in modern computing, enabling organizations to store, manipulate, and secure their data effectively. From small application
8 min read
Non-Relational Databases and Their Types
In the area of database management, the data is arranged in two ways which are Relational Databases (SQL) and Non-Relational Databases (NoSQL). While relational databases organize data into structured tables, non-relational databases use various flexible data models like key-value pairs, documents,
7 min read
What is SQL?
SQL stands for Structured Query Language. It is a standardized programming language used to manage and manipulate relational databases. It enables users to perform a variety of tasks such as querying data, creating and modifying database structures, and managing access permissions. SQL is widely use
11 min read
SQL Data Types
SQL Data Types are very important in relational databases. It ensures that data is stored efficiently and accurately. Data types define the type of value a column can hold, such as numbers, text, or dates. Understanding SQL Data Types is critical for database administrators, developers, and data ana
6 min read
SQL Operators
SQL operators are important in database management systems (DBMS) as they allow us to manipulate and retrieve data efficiently. Operators in SQL perform arithmetic, logical, comparison, bitwise, and other operations to work with database values. Understanding SQL operators is crucial for performing
6 min read
SQL Commands | DDL, DQL, DML, DCL and TCL Commands
SQL commands are crucial for managing databases effectively. These commands are divided into categories such as Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), Data Query Language (DQL), and Transaction Control Language (TCL). In this article, we will e
7 min read
Create Database in SQL
SQL CREATE DATABASE
Creating a database is one of the fundamental tasks in SQL and is the first step in structuring your data for efficient management. Whether you're a developer or a database administrator, understanding the CREATE DATABASE statement is essential. Understanding how to use this command effectively is c
6 min read
SQL DROP DATABASE
The SQL DROP DATABASE statement is an important command used to permanently delete a database from the Database Management System (DBMS). When executed, this command removes the database and all its associated objects, including tables, views, stored procedures, and other entities. In this article,
4 min read
SQL Query to Rename Database
Renaming a database in SQL is an essential task that database administrators and developers frequently perform. Whether you’re reorganizing your data, correcting naming conventions, or simply updating your project structure, knowing how to rename a database properly is critical. In this article, we'
3 min read
SQL Select Database
The USE DATABASE statement is a command in certain SQL-based database management systems that allows users to select and set a specific database as the default for the current session. By selecting a database, subsequent queries are executed within the context of that database, making it easier to i
4 min read
Tables in SQL
SQL CREATE TABLE
In SQL, creating a table is one of the most essential tasks for structuring your database. The CREATE TABLE statement defines the structure of the database table, specifying column names, data types, and constraints such as PRIMARY KEY, NOT NULL, and CHECK. Mastering this statement is fundamental to
5 min read
SQL DROP TABLE
The DROP TABLE command in SQL is a powerful and essential tool used to permanently delete a table from a database, along with all of its data, structure, and associated constraints such as indexes, triggers, and permissions. When executed, this command removes the table and all its contents, making
4 min read
SQL DELETE Statement
The SQL DELETE statement is one of the most commonly used commands in SQL (Structured Query Language). It allows you to remove one or more rows from the table depending on the situation. Unlike the DROP statement, which removes the entire table, the DELETE statement removes data (rows) from the tabl
4 min read
ALTER (RENAME) in SQL
In SQL, making structural changes to a database is often necessary. Whether it's renaming a table or a column, adding new columns, or modifying data types, the SQL ALTER TABLE command plays a critical role. This command provides flexibility to manage and adjust database schemas without affecting the
5 min read
DROP and TRUNCATE in SQL
The DROP and TRUNCATE commands in SQL are used to remove data from a table, but they work differently. Understanding the difference between these two commands is important for proper database management, especially when dealing with large amounts of data. This article provides an in-depth explanatio
5 min read
SQL Query to Create a Backup Table
Relational databases play an important role in managing data, especially during complex operations like updates and deletions. To maintain data integrity, it is essential to back up tables before making changes. SQL backup tables ensure the safety of the original dataset, allow for data recovery, an
5 min read
What is Temporary Table in SQL?
A temporary table in SQL is an important tool for maintaining intermediate results during query execution. They help store temporary data without affecting the underlying permanent tables. In this article, we’ll explore temporary tables in SQL, their types (local vs. global), and how to use them eff
3 min read
SQL ALTER TABLE
The SQL ALTER TABLE statement is a powerful tool that allows you to modify the structure of an existing table in a database. Whether you're adding new columns, modifying existing ones, deleting columns, or renaming them, the ALTER TABLE statement enables you to make changes without losing the data s
5 min read
SQL Queries
SQL SELECT Query
The select query in SQL is one of the most commonly used SQL commands to retrieve data from a database. With the select command in SQL, users can access data and retrieve specific records based on various conditions, making it an essential tool for managing and analyzing data. In this article, we’ll
4 min read
SQL TOP, LIMIT, FETCH FIRST Clause
SQL TOP, LIMIT, and FETCH FIRST clauses are used to retrieve a specific number of records from a table. These clauses are especially useful in large datasets with thousands of records. Each of these SQL clauses performs a similar operation of limiting the results returned by a query, but different d
8 min read
SQL SELECT FIRST
The SELECT FIRST clause is used in some SQL databases (primarily MS Access) to retrieve the first record from a table based on the order in which data is stored or queried. It is commonly used when you need to access just one entry, such as the first row based on the natural order or after sorting b
3 min read
SQL - SELECT LAST
SELECT LAST is a concept or function often used to describe retrieving the last record or last row from a table in SQL. Although MS Access supports a LAST() function to directly fetch the last value from a column, this function is not universally supported across all SQL-based databases. Instead, in
5 min read
SQL - SELECT RANDOM
In SQL, the RANDOM() function is used to fetch random rows from a table. It is an extremely useful function in various applications, such as selecting random users, retrieving random questions from a pool, or even for random sampling in data analysis. In this article, we will explore how to use RAND
4 min read
SQL SELECT IN Statement
The IN operator in SQL is used to compare a column's value against a set of values. It returns TRUE if the column's value matches any of the values in the specified list, and FALSE if there is no match. In this article, we will learn how IN operator works and provide practical examples to help you b
4 min read
SQL - SELECT DATE
SQL (Structured Query Language) can work with datetime data types. SELECT DATE is an important concept when retrieving records that filter data based on date. Whether you work with employee records, transaction records, or product sales, modifying and retrieving date data is often important for your
3 min read
SQL Query to Insert Multiple Rows
In SQL, the INSERT statement is used to add new records to a database table. When you need to insert multiple rows in a single query, the INSERT statement becomes efficient. In this article, We will learn different methods such as using basic INSERT statements, utilizing INSERT INTO ... SELECT for b
4 min read
SQL INSERT INTO Statement
The SQL INSERT INTO statement is one of the most commonly used commands for adding new data into a table in a database. Whether you're working with customer data, products, or user details, mastering this command is crucial for efficient database management. Let’s break down how this command works,
6 min read
SQL UPDATE Statement
In SQL, the UPDATE statement is used to modify existing records in a table. Whether you are updating a single record or multiple records at once, SQL provides the necessary functionality to make these changes. Whether you are working with a small dataset or handling large-scale databases, the UPDATE
6 min read
SQL DELETE Statement
The SQL DELETE statement is one of the most commonly used commands in SQL (Structured Query Language). It allows you to remove one or more rows from the table depending on the situation. Unlike the DROP statement, which removes the entire table, the DELETE statement removes data (rows) from the tabl
4 min read
SQL Query to Delete Duplicate Rows
Duplicate rows in a database can cause inaccurate results, waste storage space, and slow down queries. Cleaning duplicate records from our database is an essential maintenance task for ensuring data accuracy and performance. Duplicate rows in a SQL table can lead to data inconsistencies and performa
6 min read
SQL Clauses
SQL | WHERE Clause
The SQL WHERE clause allows to filtering of records in queries. Whether you're retrieving data, updating records, or deleting entries from a database, the WHERE clause plays an important role in defining which rows will be affected by the query. Without it, SQL queries would return all rows in a tab
4 min read
SQL | WITH Clause
SQL queries can sometimes be complex, especially when you need to deal with multiple nested subqueries, aggregations, and joins. This is where the SQL WITH clause also known as Common Table Expressions (CTEs) comes in to make life easier. The WITH Clause is a powerful tool that simplifies complex SQ
6 min read
SQL HAVING Clause with Examples
The HAVING clause in SQL is used to filter query results based on aggregate functions. Unlike the WHERE clause, which filters individual rows before grouping, the HAVING clause filters groups of data after aggregation. It is commonly used with functions like SUM(), AVG(), COUNT(), MAX(), and MIN().
4 min read
SQL ORDER BY
The ORDER BY clause in SQL is a powerful feature used to sort query results in either ascending or descending order based on one or more columns. Whether you're presenting data to users or analyzing large datasets, sorting the results in a structured way is essential. In this article, we’ll explain
5 min read
SQL | GROUP BY
The SQL GROUP BY clause is a powerful tool used to organize data into groups based on shared values in one or more columns. It's most often used with aggregate functions like SUM, COUNT, AVG, MIN, and MAX to perform summary operations on each group helping us extract meaningful insights from large d
5 min read
SQL LIMIT Clause
The LIMIT clause in SQL is used to control the number of rows returned in a query result. It is particularly useful when working with large datasets, allowing us to retrieve only the required number of rows for analysis or display. Whether we're looking to paginate results, find top records, or just
5 min read
SQL Operators
SQL AND and OR Operators
The SQL AND and OR operators are used to filter data based on multiple conditions. These logical operators allow users to retrieve precise results from a database by combining various conditions in SELECT, INSERT, UPDATE, and DELETE statements. In this article, we'll learn the AND and OR operators,
3 min read
SQL AND and OR Operators
The SQL AND and OR operators are used to filter data based on multiple conditions. These logical operators allow users to retrieve precise results from a database by combining various conditions in SELECT, INSERT, UPDATE, and DELETE statements. In this article, we'll learn the AND and OR operators,
3 min read
SQL LIKE Operator
The SQL LIKE operator is used for performing pattern-based searches in a database. It is used in combination with the WHERE clause to filter records based on specified patterns, making it essential for any database-driven application that requires flexible search functionality. In this article, we w
5 min read
SQL IN Operator
The SQL IN operator filters data based on a list of specific values. In general, we can only use one condition in the Where clause, but the IN operator allows us to specify multiple values. In this article, we will learn about the IN operator in SQL by understanding its syntax and examples. IN Opera
4 min read
SQL NOT Operator
The SQL NOT Operator is a logical operator used to negate or reverse the result of a condition in SQL queries. It is commonly used with the WHERE clause to filter records that do not meet a specified condition, helping you exclude certain values from your results. In this article, we will learn ever
3 min read
SQL NOT EQUAL Operator
The SQL NOT EQUAL operator is a comparison operator used to check if two expressions are not equal to each other. It helps filter out records that match certain conditions, making it a valuable tool in SQL queries. In this article, We will explore the SQL NOT EQUAL operator, including its syntax, us
4 min read
SQL IS NULL
The SQL IS NULL operator is a logical operator used to identify and filter out rows with NULL values in a column. A NULL value represents missing or undefined data in a database. It is different from a zero value or blank space, and it indicates that the value is unknown. In this article, we will le
4 min read
SQL UNION Operator
The SQL UNION operator is used to combine the result sets of two or more SELECT queries into a single result set. It is a powerful tool in SQL that helps aggregate data from multiple tables, especially when the tables have similar structures. In this guide, we'll explore the SQL UNION operator, how
4 min read
SQL UNION ALL
UNION ALL Operator is used to combine the results of two or more SELECT statements into a single result set. Unlike the UNION operator, which eliminates duplicate records and UNION ALL includes all duplicates. This makes UNION ALL it faster and more efficient when we don't need to remove duplicates.
4 min read
SQL | Except Clause
The SQL EXCEPT operator is used to return the rows from the first SELECT statement that are not present in the second SELECT statement. This operator is conceptually similar to the subtract operator in relational algebra. It is particularly useful for excluding specific data from your result set. In
4 min read
SQL BETWEEN Operator
The BETWEEN operator in SQL is used to filter records within a specific range. Whether applied to numeric, text, or date columns it simplifies the process of retrieving data that falls within a particular boundary. In this article, we will explore the SQL BETWEEN operator with examples. SQL BETWEEN
3 min read
SQL | ALL and ANY
In SQL, the ALL and ANY operators are logical operators used to compare a value with a set of values returned by a subquery. These operators provide powerful ways to filter results based on a range of conditions. In this article, we will explore ALL and ANY in SQL, their differences, and how to use
4 min read
SQL | ALL and ANY
In SQL, the ALL and ANY operators are logical operators used to compare a value with a set of values returned by a subquery. These operators provide powerful ways to filter results based on a range of conditions. In this article, we will explore ALL and ANY in SQL, their differences, and how to use
4 min read
SQL | INTERSECT Clause
In SQL, the INTERSECT clause is used to retrieve the common records between two SELECT queries. It returns only the rows that are present in both result sets. This makes INTERSECT an essential clause when we need to find overlapping data between two or more queries. In this article, we will explain
5 min read
SQL | EXISTS
The SQL EXISTS condition is used to test whether a correlated subquery returns any results. If the subquery returns at least one row, the EXISTS condition evaluates to TRUE; otherwise, it evaluates to FALSE. The EXISTS operator can be used in various SQL statements like SELECT, UPDATE, INSERT, and D
3 min read
SQL CASE Statement
The CASE statement in SQL is a versatile conditional expression that enables us to incorporate conditional logic directly within our queries. It allows you to return specific results based on certain conditions, enabling dynamic query outputs. Whether you need to create new columns, modify existing
4 min read
SQL Aggregate Functions
SQL Aggregate functions
SQL Aggregate Functions are used to perform calculations on a set of rows and return a single value. These functions are particularly useful when we need to summarize, analyze, or group large datasets in SQL databases. Whether you're working with sales data, employee records, or product inventories,
4 min read
SQL COUNT(), AVG() and SUM() Function
SQL aggregate functions, such as COUNT(), AVG(), and SUM(), are essential tools for performing mathematical analysis on data. These functions allow you to gather valuable insights from your database, such as calculating totals, and averages, and counting specific rows. In this article, we’ll explain
3 min read
SQL COUNT(), AVG() and SUM() Function
SQL aggregate functions, such as COUNT(), AVG(), and SUM(), are essential tools for performing mathematical analysis on data. These functions allow you to gather valuable insights from your database, such as calculating totals, and averages, and counting specific rows. In this article, we’ll explain
3 min read
SQL MIN() and MAX() Functions
The SQL MIN() and MAX() functions are essential aggregate functions in SQL used for data analysis. They allow you to extract the minimum and maximum values from a specified column, respectively, making them invaluable when working with numerical, string, or date-based data. In this article, we will
4 min read
SQL MIN() and MAX() Functions
The SQL MIN() and MAX() functions are essential aggregate functions in SQL used for data analysis. They allow you to extract the minimum and maximum values from a specified column, respectively, making them invaluable when working with numerical, string, or date-based data. In this article, we will
4 min read
SQL COUNT(), AVG() and SUM() Function
SQL aggregate functions, such as COUNT(), AVG(), and SUM(), are essential tools for performing mathematical analysis on data. These functions allow you to gather valuable insights from your database, such as calculating totals, and averages, and counting specific rows. In this article, we’ll explain
3 min read
SQL Data Constraints
SQL NOT NULL Constraint
In SQL, constraints are used to enforce rules on data, ensuring the accuracy, consistency, and integrity of the data stored in a database. One of the most commonly used constraints is the NOT NULL constraint, which ensures that a column cannot have NULL values. This is important for maintaining data
3 min read
SQL | UNIQUE Constraint
In SQL, constraints play a vital role in maintaining the integrity and accuracy of the data stored in a database. One such constraint is the UNIQUE constraint, which ensures that all values in a column (or a combination of columns) are distinct, preventing duplicate entries. This constraint is espec
4 min read
SQL PRIMARY KEY Constraint
The PRIMARY KEY constraint in SQL is one of the most important constraints used to ensure data integrity in a database table. A primary key uniquely identifies each record in a table, preventing duplicate or NULL values in the specified column(s). Understanding how to properly implement and use the
5 min read
SQL FOREIGN KEY Constraint
A FOREIGN KEY constraint is a fundamental concept in relational databases, ensuring data integrity by enforcing relationships between tables. By linking a child table to a parent table, the foreign key establishes referential integrity. This constraint ensures that the values in the foreign key colu
5 min read
Composite Key in SQL
A composite key is a primary key that is made up of more than one column to uniquely identify records in a table. Unlike a single-column primary key, a composite key combines two or more columns to ensure uniqueness. While any of the individual columns in a composite key might not be unique on their
2 min read
SQL | UNIQUE Constraint
In SQL, constraints play a vital role in maintaining the integrity and accuracy of the data stored in a database. One such constraint is the UNIQUE constraint, which ensures that all values in a column (or a combination of columns) are distinct, preventing duplicate entries. This constraint is espec
4 min read
SQL - ALTERNATE KEY
Alternate Key is any candidate key not selected as the primary key. So, while a table may have multiple candidate keys (sets of columns that could uniquely identify rows), only one of them is designated as the Primary Key. The rest of these candidate keys become Alternate Keys. In other words, we ca
4 min read
SQL | CHECK Constraint
In SQL, One such constraint is the CHECK constraint, which allows to enforcement of domain integrity by limiting the values that can be inserted or updated in a column. By using CHECK, we can define conditions on a column’s values and ensure that they adhere to specific rules. In this article, we wi
5 min read
SQL | DEFAULT Constraint
In SQL, maintaining data integrity and ensuring consistency across tables is important for effective database management. One way to achieve this is by using constraints. Among the many types of constraints, the DEFAULT constraint plays an important role in automating data insertion and ensuring tha
3 min read
SQL Joining Data
SQL Joins (Inner, Left, Right and Full Join)
SQL joins are fundamental tools for combining data from multiple tables in relational databases. Joins allow efficient data retrieval, which is essential for generating meaningful observations and solving complex business queries. Understanding SQL join types, such as INNER JOIN, LEFT JOIN, RIGHT JO
6 min read
SQL Outer Join
SQL Outer Joins allow retrieval of rows from two or more tables based on a related column. Unlike inner Joins, they also include rows that do not have a corresponding match in one or both of the tables. This capability makes Outer Joins extremely useful for comprehensive data analysis and reporting,
4 min read
SQL LEFT JOIN
In SQL, LEFT JOIN retrieves all records from the left table and only the matching records from the right table. When there is no matching record found, NULL values are returned for columns from the right table. This makes LEFT JOIN extremely useful for queries where you need to retain all records fr
5 min read
SQL RIGHT JOIN
In SQL, the RIGHT JOIN (also called RIGHT OUTER JOIN) is an essential command used to combine data from two tables based on a related column. It returns all records from the right table, along with the matching records from the left table. If there is no matching record in the left table, SQL will r
4 min read
SQL FULL JOIN
In SQL, the FULL JOIN (or FULL OUTER JOIN) is a powerful technique used to combine records from two or more tables. Unlike an INNER JOIN, which only returns rows where there are matches in both tables, a FULL JOIN retrieves all rows from both tables, filling in NULL values where matches do not exist
4 min read
SQL CROSS JOIN
In SQL, the CROSS JOIN is a unique join operation that returns the Cartesian product of two or more tables. This means it matches each row from the left table with every row from the right table, resulting in a combination of all possible pairs of records. In this article, we will learn the CROSS JO
3 min read
SQL Self Join
A Self Join in SQL is a powerful technique that allows one to join a table with itself. This operation is helpful when you need to compare rows within the same table based on specific conditions. A Self Join is often used in scenarios where there is hierarchical or relational data within the same ta
4 min read
SQL | UPDATE with JOIN
In SQL, the UPDATE with JOIN statement is a powerful tool that allows updating one table using data from another table based on a specific JOIN condition. This technique is particularly useful when we need to synchronize data, merge records, or update specific columns in one table by referencing rel
4 min read
SQL DELETE JOIN
The SQL DELETE JOIN statement is a powerful feature that allows us to delete rows from one table based on conditions involving another table. This is particularly useful when managing relationships between tables in a database. For example, we may want to delete rows in a "Library Books" table where
4 min read
Recursive Join in SQL
In SQL, a recursive join is a powerful technique used to handle hierarchical data relationships, such as managing employee-manager relationships, family trees, or any data with a self-referential structure. This type of join enables us to combine data from the same table repeatedly, accumulating rec
3 min read