**Course Title:** SQLite Mastery: Lightweight Database Management **Section Title:** Introduction to SQLite and Relational Databases **Topic:** Introduction to basic SQL commands in SQLite: SELECT, FROM, WHERE Welcome to this topic, where you'll learn the fundamental SQL commands used in SQLite to interact with relational databases. By the end of this topic, you'll have a solid understanding of the SELECT, FROM, and WHERE clauses, and how to apply them in real-world scenarios. ### Understanding SQL SQL (Structured Query Language) is a standard programming language used to manage and manipulate relational databases. In SQLite, SQL is used to create, modify, and query databases. Don't worry if you're new to SQL – we'll break down the basics in this topic. ### Basic SQL Commands: SELECT, FROM, WHERE Let's dive into the three fundamental SQL commands you need to know: SELECT, FROM, and WHERE. ### 1. SELECT Command The SELECT command is used to retrieve specific data from a database. It's used to select data from one or more tables in a database. **Basic Syntax:** ```sql SELECT column1, column2, ... FROM tablename; ``` In the above syntax: * `SELECT` is the keyword used to select data. * `column1`, `column2`, etc. are the columns you want to retrieve data from. * `FROM` specifies the table(s) to retrieve data from. * `tablename` is the name of the table(s) from which you want to retrieve data. **Example:** ```sql SELECT name, email FROM customers; ``` This query will retrieve the `name` and `email` columns from the `customers` table. ### 2. FROM Command The FROM command is used to specify the table(s) to retrieve data from. You can specify one or more tables in the FROM clause. **Basic Syntax:** ```sql SELECT column1, column2, ... FROM table1, table2, ...; ``` In the above syntax: * `SELECT` is the keyword used to select data. * `column1`, `column2`, etc. are the columns you want to retrieve data from. * `FROM` specifies the table(s) to retrieve data from. * `table1`, `table2`, etc. are the names of the tables from which you want to retrieve data. **Example:** ```sql SELECT orders.order_id, customers.name FROM orders, customers WHERE orders.customer_id = customers.customer_id; ``` This query will retrieve the `order_id` from the `orders` table and the `name` from the `customers` table, where the `customer_id` matches in both tables. ### 3. WHERE Command The WHERE command is used to filter data based on conditions. It's used to specify a condition that the data must meet in order to be included in the result set. **Basic Syntax:** ```sql SELECT column1, column2, ... FROM tablename WHERE condition; ``` In the above syntax: * `SELECT` is the keyword used to select data. * `column1`, `column2`, etc. are the columns you want to retrieve data from. * `FROM` specifies the table(s) to retrieve data from. * `tablename` is the name of the table(s) from which you want to retrieve data. * `WHERE` specifies the condition that the data must meet. * `condition` is the condition that must be met. **Example:** ```sql SELECT name, email FROM customers WHERE country = 'USA'; ``` This query will retrieve the `name` and `email` columns from the `customers` table, where the `country` is 'USA'. ### Combining SELECT, FROM, and WHERE Commands Now that you've learned the basic syntax of the SELECT, FROM, and WHERE commands, let's see how to combine them: ```sql SELECT column1, column2, ... FROM table1, table2, ... WHERE condition; ``` **Example:** ```sql SELECT orders.order_id, customers.name FROM orders, customers WHERE orders.customer_id = customers.customer_id AND country = 'USA'; ``` This query will retrieve the `order_id` from the `orders` table and the `name` from the `customers` table, where the `customer_id` matches in both tables and the `country` is 'USA'. ### Key Concepts * **SELECT**: used to select specific data from a database. * **FROM**: used to specify the table(s) to retrieve data from. * **WHERE**: used to filter data based on conditions. ### Practical Takeaways * Use the SELECT command to retrieve specific data from a database. * Use the FROM command to specify the table(s) to retrieve data from. * Use the WHERE command to filter data based on conditions. * Combine the SELECT, FROM, and WHERE commands to retrieve specific data from a database based on conditions. ### Resources * [SQLite Documentation](https://www.sqlite.org/docs.html) (official documentation) * [W3Schools SQL Tutorial](https://www.w3schools.com/sql/) (interactive SQL tutorial) ### Next Topic In the next topic, we'll learn about creating and managing SQLite databases and tables. **Leave a Comment/Ask for Help** If you have any questions or need help with understanding the material, please leave a comment below. **Comment Box:** (Note: There is no comment box in this text format. However, you can assume that a comment box is present below the content where readers can leave their comments and ask for help.)