SELECT specific columns in SQL - 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 returns only the 'name' and 'age' columns for all rows.

beginner

What happens if you use SELECT * in a query?

It selects all columns from the table, returning every column for each row.

beginner

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

Selecting specific columns reduces the amount of data returned, making queries faster and easier to read.

beginner

Write a SQL query to select the columns 'product_id' and 'price' from a table named 'products'.

The query is: SELECT product_id, price FROM products;

Which SQL keyword is used to choose specific columns from a table?

A SELECT

B WHERE

C FROM

D INSERT

The SELECT keyword is used to specify which columns to retrieve.

What does SELECT * do?

A Selects all rows but no columns

B Selects all columns from the table

C Deletes all data

D Updates all columns

SELECT * returns every column for each row in the table.

How do you select only the 'email' column from a table named 'users'?

A SELECT email FROM users;

B SELECT * FROM users WHERE email;

C SELECT users FROM email;

D SELECT email WHERE users;

The correct syntax is SELECT email FROM users; to get only the email column.

Why is it better to select specific columns instead of using SELECT *?

A It makes queries slower

B It changes the table structure

C It returns less data and improves performance

D It deletes unnecessary columns

Selecting specific columns reduces data size and speeds up query results.

Which of these is a valid SQL query to select columns 'id' and 'name' from 'employees'?

A SELECT id name FROM employees;

B SELECT employees FROM id, name;

C SELECT * id, name FROM employees;

D SELECT id, name FROM employees;

Option D uses correct syntax to select specific columns.

Explain how to select specific columns from a table in SQL and why it is useful.

Think about choosing only what you need from a list.

Write a SQL query to get the 'title' and 'author' columns from a 'books' table.

Use the format: SELECT columns FROM table;