Inserting Records · Updating Records · Deleting Records Modifying data—adding new rows, updating existing ones, and removing obsolete entries—is the flip side of querying. Without the ability to change data, databases become static archives. In this detailed guide, you’ll learn step by step how to insert, update, and delete records safely and efficiently in a relational database. Inserting Records Every database starts empty. The INSERT statement populates tables with new rows. You’ll discover how to add single records, bulk load data from other queries, and handle conflicts or defaults. 1. Single-Row Inserts Use INSERT INTO … VALUES to add one row at a time. Always specify the column list to avoid mismatches when the schema changes. sql INSERT INTO employees (first_name, last_name, email, hire_date, salary) VALUES ('Jane', 'Doe', 'jane.doe@example.com', '2025-08-15', 60000); Key points: Match the order of columns and values exactly. Omit columns wit...
Lesson 5.5 – Basic Statistics (AVERAGE, MEDIAN, MODE) Basic statistical functions help you understand the central tendency of your data. Excel provides simple functions to calculate the average value, the middle value, and the most frequent value in a dataset. These functions are widely used in business, finance, education, and data analysis. 1. What Are Basic Statistics? Basic statistics summarize your data and help you understand its general behavior. The three most common measures are: AVERAGE – The arithmetic mean MEDIAN – The middle value MODE – The most frequent value These functions are essential for analyzing trends, comparing groups, and making decisions. 2. AVERAGE Function The AVERAGE function calculates the mean of a group of numbers. Syntax: =AVERAGE(range) Example: =AVERAGE(B2:B10) Use AVERAGE when you want a general idea of the typical value in your dataset. 3. MEDIAN Function The MEDIAN functio...