Method 1: Using LIMIT (MySQL, PostgreSQL) Explanation: Method 2: Using Subquery (Works in most databases) Explanation: Method 3: Using DENSE_RANK() (SQL Server, Oracle, PostgreSQL) Explanation: For interviews, Method 2 (Subquery) and Method 3 (Window Function) are the most commonly asked.
If you are learning SQL, you might come across the term trigger. A trigger in SQL is a special type of stored procedure that automatically executes or fires when certain events occur in a database table, such as INSERT, UPDATE, or DELETE operations. Triggers are very useful for maintaining data integrity, automatically updating related tables, … Read more
When learning SQL, you may hear the term SQL Stored Procedure. Many freshers get confused: Is it a function? Is it a query? Don’t worry — in this blog, we will explain what a stored procedure is, why we use it, and how it works with simple examples. What is a Stored Procedure? Example: Now, … Read more
When you start learning SQL, you often hear about Views. Many freshers get confused thinking – Are views like tables? In this blog, we will explain what are views in SQL in very simple words that any beginner in India can understand. What is a View in SQL? Example: Now whenever you use SELECT * … Read more
If you are a fresher learning SQL, you might get confused between UNION and UNION ALL. Don’t worry, in this blog we will explain the difference between UNION and UNION ALL in SQL with very simple examples that any beginner in India can understand. What is UNION? Example: This will remove duplicates and show only … Read more
GROUP BY Example: Student Subject Marks Raju Math 80 Pooja Math 90 Amit Science 70 Neha Science 60 Output: So GROUP BY = Group then summarize. ORDER BY Example: Output: So ORDER BY = Sorting (like arrange in queue). Quick Analogy (Cricket Example): Imagine a cricket match scoreboard. Super-Simple Recap for Freshers:
Aggregate = “Total / Summary”. In SQL, aggregate functions are used to calculate values from multiple rows together (instead of checking each row one by one). Example: In a class of students, instead of checking every student’s marks separately, we calculate total marks, average marks, highest marks, etc. Common Aggregate Functions: Real-Life Analogy (Cricket Example): … Read more
Imagine you have a big dictionary .If you want to find the meaning of the word “Cricket”, In SQL, Index = shortcut for the database to find data faster. What are Indexes? Types of Indexes in SQL: Quick Recap for Freshers:
Constraints are like rules we put on a table’s columns to control what kind of data can go inside. Think of it like traffic rules: Types of Constraints (with Simple Examples) NOT NULL Means the column cannot be empty.Like in college admission form → Name is mandatory. Example: You must enter a name, otherwise error. … Read more
What is Denormalization? Example: Imagine you have a normalized database with these two tables: 1. Students Table StudentID Name ClassID 1 Rahul 101 2 Priya 102 2. Classes Table ClassID ClassName 101 Maths 102 Science his is normalized (no repeated data). But if you want to show a list of students with their class name, … Read more