Performing Smart Analytics and AI on GCP: What Does the Asterisk (*) Mean in SQL Queries and Why Is It Important for Data Selection?

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Question

What does the asterisk (*) symbol mean in SQL?

A. You want to select the first record of a table.
B. You want to merge the data from two tables together.
C. You want to select all of the columns for a specific table in their defined order.
D. You are retrieving the number of columns for a specific table.

Answer

C. You want to select all of the columns for a specific table in their defined order.

Explanation

The asterisk (*) symbol in SQL is used to select all columns from a specified table in their defined order. When placed after the SELECT keyword in an SQL query, it serves as a wildcard that tells the database to return every column available in the table without having to list each column name individually.

How the Asterisk Works in SQL

When you use the asterisk in a SELECT statement like SELECT * FROM customers;, the database engine interprets this command to retrieve all columns from the customers table in their original defined order. This is particularly useful in several scenarios:

• When you need to quickly view all data in a table
• During exploratory data analysis when you’re unfamiliar with a table’s structure
• When writing initial query drafts before refining column selection

The asterisk is essentially a shorthand notation that saves you from typing out every column name, which can be especially valuable for tables with many columns.

Examples of Using the Asterisk in SQL

SELECT * FROM books;
SELECT * FROM products;
SELECT * FROM users;

Each of these queries would return all columns from their respective tables. For example, if the books table had columns like id, title, author, and publication_date, the query would return all these columns for each record in the table.

Important Considerations When Using the Asterisk

While convenient, using the asterisk has some important implications:

• Performance impact: Retrieving all columns when you only need a few can unnecessarily increase data transfer and processing time
• Code readability: Explicitly naming columns makes code more self-documenting
• Stability: If table structure changes (adding/removing columns), queries using * will return different results

Other SQL Uses of the Asterisk Symbol

Beyond column selection, the asterisk has other uses in SQL:

• In COUNT(*) functions to count all rows (including nulls and duplicates)
• As a multiplication operator in arithmetic expressions
• In GRANT and REVOKE statements to represent all privileges, tables, or users
• As part of pattern matching expressions with wildcards

The correct answer is indeed C: You want to select all of the columns for a specific table in their defined order.

Google Cloud Certification Tip: Understanding SQL fundamentals, including the asterisk usage, is important when working with database solutions on Google Cloud Platform, especially when using services like BigQuery, Cloud SQL, or other data processing products.

Performing Smart Analytics and AI on Google Cloud Platform skill assessment practice question and answer (Q&A) dump including multiple choice questions (MCQ) and objective type questions, with detail explanation and reference available free, helpful to pass the Performing Smart Analytics and AI on Google Cloud Platform exam and earn Performing Smart Analytics and AI on Google Cloud Platform certification.