SELECT all columns in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SQL query SELECT * FROM table_name; do?

It selects and returns all columns and all rows from the table named table_name.

beginner

In SQL, what symbol is used to select all columns from a table?

The asterisk symbol * is used to select all columns.

intermediate

Why might you want to avoid using SELECT * in large databases?

Because it returns all columns, which can be slow and use more resources if the table has many columns or rows. Selecting only needed columns is more efficient.

beginner

Write a SQL query to select all columns from a table named employees.

SELECT * FROM employees;

beginner

What is the difference between SELECT * and SELECT column1, column2?

SELECT * returns all columns, while SELECT column1, column2 returns only the specified columns.

What does the asterisk (*) mean in the SQL query SELECT * FROM customers;?

A Select all columns from the customers table

B Select all rows from the customers table

C Select only the first column from the customers table

D Delete all data from the customers table

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

Which SQL query selects all columns from the table named orders?

A SELECT columns FROM orders;

B SELECT all FROM orders;

C SELECT * FROM orders;

D SELECT orders.*;

The correct syntax to select all columns is SELECT * FROM table_name;

If you want to select only the columns 'name' and 'age' from a table, which query is correct?

A SELECT * FROM table_name;

B SELECT name AND age FROM table_name;

C SELECT name age FROM table_name;

D SELECT name, age FROM table_name;

To select specific columns, list them separated by commas after SELECT.

What is a potential downside of using SELECT * in a query?

A It only returns one row

B It can slow down the query by returning unnecessary data

C It deletes data from the table

D It requires specifying column names

Selecting all columns can return more data than needed, slowing down performance.

Which part of the SQL query specifies the table to select data from?

A FROM

B WHERE

C SELECT

D ORDER BY

The FROM clause specifies the table to select data from.

Explain how to select all columns from a table in SQL and why you might want to be careful using it.

Think about the * symbol and performance.

Write a simple SQL query to get all data from a table called 'products'.

Use the wildcard * to select all columns.