AK TECH CODING

When working with databases, understanding key constraints is essential for ensuring data integrity. In this post, I’ll explain what a PRIMARY KEY is, how it differs from a UNIQUE KEY , and when to use them. 1. What is a PRIMARY KEY? A PRIMARY KEY is a column (or a set of columns) in a table that uniquely identifies each row. It ensures that no two rows have the same primary key value and that the key value is not null. Key Characteristics of PRIMARY KEY: Uniquely identifies each row in a table. Cannot contain NULL values. A table can only have one PRIMARY KEY . Example: -- Defining a PRIMARY KEY on 'customer_id' CREATE TABLE customers ( customer_id INT PRIMARY KEY, name VARCHAR(100), email VARCHAR(100) ); 2. What is a UNIQUE KEY? A UNIQUE KEY constraint also ensures that all values in a column (or a set of columns) are unique. However, unlike the primary key, a unique key can contain NULL values, and a table can have multiple unique keys....

When working with databases, SQL query performance is crucial. A slow query can make your application sluggish and affect the overall user experience. In this post, I’ll explain how to optimize SQL queries with simple tips that anyone can understand! 1. Use SELECT Fields Instead of SELECT * It’s tempting to use SELECT * to grab all the data from a table, but this can slow down your query, especially if the table has a lot of columns. Instead, only select the columns you need. Example: -- Avoid this SELECT * FROM customers; -- Do this SELECT name, email FROM customers; 2. Use WHERE Clauses to Filter Data Always use a WHERE clause to filter data and reduce the number of rows the database has to process. This can make a huge difference, especially when dealing with large tables. Example: -- Without filtering SELECT * FROM orders; -- With filtering SELECT * FROM orders WHERE status = 'Shipped'; 3. Avoid Using Functions in WHERE Clauses Using functions in a WHERE ...

When working with databases, you often need to get information from more than one table. This is where joins come in! Joins allow you to combine rows from two or more tables based on a common column between them. In this blog, I’ll explain what joins are and go over the main types with simple examples.

Introduction When working with a database, you often need to store text, such as names, addresses, or descriptions. SQL offers different types of text storage: CHAR , VARCHAR , NCHAR , and NVARCHAR . Although they all store text, they differ in how they store and handle data. Understanding these differences can help you make the right choice and optimize your database.

When working with SQL, two common types of subprograms you’ll come across are Functions and Procedures . Both are used to perform specific tasks and encapsulate SQL code, but they serve different purposes and have important differences. Let's explore these in detail to help you understand when and why you would use each.