Select Statement in MySQL | Beginner MySQL Series

Summary

This tutorial delves into the SELECT statement in MySQL, essential for querying databases. It teaches how to specify columns, use the asterisk to select all columns, and limit results. The video covers executing queries, the importance of specifying databases, and handling calculations with MySQL's adherence to PEMDAS. It also introduces the DISTINCT keyword for unique values and the practicality of saving queries for future use, setting the stage for the WHERE statement in subsequent lessons.

Takeaways

• 😀 The SELECT statement in MySQL is used to specify which columns to retrieve from a database table.
• 🔍 The asterisk (*) symbol in a SELECT statement represents all columns in the specified table.
• 🚀 To limit the number of rows returned, use the LIMIT clause, which can be adjusted based on the dataset size.
• ⚙️ It's important to specify the database before the table name, especially when working with multiple databases, to avoid errors.
• 📝 Including a semicolon at the end of a query signifies the end of the statement in MySQL.
• 👤 The SELECT statement allows for selecting specific columns or using functions and calculations within the query.
• 🔢 MySQL follows the PEMDAS order of operations (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction) for mathematical calculations in queries.
• 📊 The DISTINCT keyword is used to return only unique values from a specified column or a combination of columns.
• 💾 Saving queries in MySQL can be done through the interface, allowing for easy access and sharing of code.
• ➡️ The tutorial also briefly touches on the importance of organizing and saving code, setting the stage for future lessons on more advanced SQL topics.

Q & A

What is the primary function of the SELECT statement in MySQL?

The SELECT statement in MySQL is used to work with columns and specify which columns should be displayed in the output.

How do you specify a table to query in MySQL?

You specify a table to query by using the SELECT statement followed by the table name, for example, 'SELECT * FROM employee_demographics'.

What does the asterisk (*) symbol represent in a SELECT statement?

The asterisk (*) symbol in a SELECT statement represents all columns in the specified table.

Why is it important to include a semicolon at the end of a MySQL query?

A semicolon is used to indicate the end of a MySQL query, allowing the system to distinguish between multiple queries when they are written consecutively.

What is the purpose of the LIMIT clause in a SELECT statement?

The LIMIT clause is used to restrict the number of rows returned by a SELECT statement, which can help manage processing time and reduce the load on the system.

Why might you need to specify the database before the table name in a query?

Specifying the database before the table name is important when working with multiple databases to ensure that the query is executed against the correct database, especially if the table names are not unique across databases.

How can you select specific columns from a table in MySQL?

You can select specific columns by listing their names after the SELECT keyword, separated by commas, instead of using the asterisk (*) to select all columns.

What does the DISTINCT keyword do in a MySQL SELECT statement?

The DISTINCT keyword is used to return only unique values from a specified column or set of columns, eliminating duplicates from the output.

How does MySQL handle mathematical calculations in the SELECT statement?

MySQL follows the order of operations defined by PEMDAS (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction) when performing calculations in the SELECT statement.

What is the significance of the comment symbol (#) in MySQL?

The comment symbol (#) in MySQL is used to add notes or comments within the code that will not be executed. It helps in documentation and clarification without affecting the query execution.

How can you save your MySQL queries for future use or sharing?

You can save your MySQL queries by using the save function in the editor or interface you are using, typically by clicking a save button and specifying a file name.