Selecting specific columns in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SQL SELECT statement do?

The SELECT statement retrieves data from a database table. You can choose to get all columns or specific columns.

beginner

How do you select only the 'name' and 'age' columns from a table called 'people'?

Use: SELECT name, age FROM people; This gets only the 'name' and 'age' columns from the 'people' table.

beginner

What happens if you use SELECT * in a query?

The * means 'all columns'. So, SELECT * returns every column in the table.

beginner

Can you select columns in any order you want?

Yes! You can list columns in any order in the SELECT statement. The result will show columns in that order.

beginner

Why might you want to select specific columns instead of all columns?

Selecting specific columns can make queries faster and results easier to read. It also reduces data sent over the network.

Which SQL query selects only the 'email' column from the 'users' table?

A SELECT email FROM users;

B SELECT * FROM users;

C SELECT users FROM email;

D SELECT email, users;

Only option D correctly selects the 'email' column from the 'users' table.

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

A Select no columns

B Select only one column

C Select all columns

D Select columns with * in their name

The asterisk (*) means to select all columns from the table.

How would you select the columns 'first_name' and 'last_name' from a table 'employees'?

A SELECT first_name last_name FROM employees;

B SELECT employees FROM first_name, last_name;

C SELECT * FROM employees WHERE first_name, last_name;

D SELECT first_name, last_name FROM employees;

Option D correctly lists the columns separated by a comma after SELECT.

If you want to see columns in a different order, what should you do?

A Use ORDER BY clause

B List columns in the desired order in the SELECT statement

C Change the table structure

D You cannot change column order

You control the order of columns in the result by listing them in that order in the SELECT statement.

Why is it better to select only needed columns?

A To improve query speed and reduce data size

B To confuse users

C To delete other columns

D To rename columns automatically

Selecting only needed columns makes queries faster and results smaller.

Explain how to select specific columns from a table in SQL.

Think about the basic structure of a SELECT query.

Why might you choose to select specific columns instead of all columns?

Consider what happens when you get too much data.