**Course Title:** SQLite Mastery: Lightweight Database Management **Section Title:** Basic Data Retrieval and Filtering **Topic:** Using SELECT statements for querying data **Introduction** In the previous topics, we covered the basics of SQLite and relational databases, created and managed databases and tables, and understood data types and primary and foreign keys. Now, we will dive into the world of data retrieval and filtering using the SELECT statement. In this topic, we will explore the SELECT statement in-depth, learn how to use it to retrieve data from a database, and practice with examples. **What is a SELECT statement?** A SELECT statement is a SQL command used to retrieve data from one or more tables in a database. It is one of the most commonly used SQL commands, and it allows you to specify the data you want to retrieve, filter it, and format the output. **Basic syntax of a SELECT statement** The basic syntax of a SELECT statement is as follows: ```sql SELECT column1, column2, ... FROM tablename; ``` In this syntax: * `column1`, `column2`, etc., are the names of the columns you want to retrieve. * `tablename` is the name of the table from which you want to retrieve the data. **Retrieving all columns using the asterisk (*)** Instead of specifying each column name, you can use an asterisk (*) to retrieve all columns. Here's how to do it: ```sql SELECT * FROM tablename; ``` **Retrieving specific columns** You can retrieve specific columns by listing their names in the SELECT clause. Here's an example: ```sql SELECT first_name, last_name, age FROM customers; ``` **Retrieving distinct values** To retrieve distinct values, you can use the DISTINCT keyword. Here's an example: ```sql SELECT DISTINCT country FROM customers; ``` **Using aliases** An alias is a temporary name given to a column or table within the scope of a query. You can use aliases to make your query output more readable. Here's an example: ```sql SELECT first_name AS "First Name", last_name AS "Last Name" FROM customers; ``` **Using aggregate functions** Aggregate functions are used to perform calculations on a set of values. Examples of aggregate functions include SUM, COUNT, AVG, MAX, and MIN. Here's an example: ```sql SELECT SUM(price) AS total_price FROM orders; ``` **Grouping data** You can group data using the GROUP BY clause. The GROUP BY clause groups a set of rows into a set of summary rows based on the values in one or more columns. Here's an example: ```sql SELECT country, COUNT(*) AS num_customers FROM customers GROUP BY country; ``` **Having clause** The HAVING clause is used in combination with the GROUP BY clause to filter groups of rows based on the values of one or more columns. Here's an example: ```sql SELECT country, COUNT(*) AS num_customers FROM customers GROUP BY country HAVING COUNT(*) > 10; ``` **Practice time** Use the following database schema and data to practice what you've learned: .tables customers and orders schema along with sample data: [SQLite Tutorial by sqlite.org](https://www.sqlite.org/tutorial.html "SQLite Tutorial") **Conclusion** In this topic, we covered the basics of using SELECT statements for querying data. We learned how to retrieve all columns, specific columns, distinct values, and use aliases, aggregate functions, grouping, and having clauses. With this knowledge, you're ready to start retrieving data from a database using the SELECT statement. **Try it yourself** Create a database and table, insert some data, and practice using the SELECT statement to retrieve the data. Use the concepts you've learned in this topic to create different queries and observe the results. **Need help?** If you have any questions or need help with a query, feel free to leave a comment below and I'll be happy to assist you.