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Performing Smart Analytics and AI on GCP: What SQL Command Links Two Tables for Value Comparison?

By: Author Alex Lim

Posted on

Categories Performing Smart Analytics and AI on GCP

Discover how the SQL JOIN command is used to link two tables for value comparison in relational databases. Learn about its syntax, types, and practical examples to enhance your SQL skills.

Question

What SQL command can reference two different tables to one another to compare values?

A. APPEND
B. JOIN
C. INTERSECT
D. MERGE

Answer

B. JOIN

Explanation

The SQL JOIN command is used to combine rows from two or more tables based on a related column between them. This allows you to compare values across tables and retrieve meaningful results. Here’s why JOIN is the correct choice:

Purpose of JOIN

The JOIN clause establishes a relationship between two tables by specifying a condition (e.g., matching values in specific columns) that links their data.

For example, if you have an Orders table and a Customers table, you can use a JOIN to retrieve orders along with customer details.

Types of JOINs

  • INNER JOIN: Retrieves rows where there is a match in both tables.
  • LEFT JOIN: Includes all rows from the left table and matched rows from the right table.
  • RIGHT JOIN: Includes all rows from the right table and matched rows from the left.
  • FULL OUTER JOIN: Combines results from both tables, including unmatched rows with NULL values.

Syntax Example

SELECT table1.column1, table2.column2
FROM table1
JOIN table2
ON table1.common_column = table2.common_column;

This query retrieves data where the common_column in both tables matches.

Comparison with Other Options

APPEND (A): Adds new rows to an existing table but does not compare values or link tables.

INTERSECT (C): Returns common rows between two result sets but does not establish relationships between tables.

MERGE (D): Combines datasets but is typically used for data manipulation rather than querying relationships.

By using JOIN, you can effectively compare and combine data across multiple tables, making it an essential SQL command for relational database operations.

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.