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 ...