Solution:Step 1: Understand LEFT JOINLEFT JOIN returns all rows from the left table (Author) and matching rows from the right table (AuthorBio).Step 2: Check for missing matchesIf an author has no biography, AuthorBio.Biography will be NULL.Final Answer:All authors with their biographies; NULL if no

[Solved] Given these tables:CREATE TABLE Author (AuthorID INT PRIMARY KEY, Name VARCHAR(50));CREATE TABLE AuthorBio (AuthorID INT PRIMARY KEY, Biography TEXT, FOREIGN KEY (AuthorID) REFERENCES... | SQL

SQL - Table Relationships

Given these tables:

CREATE TABLE Author (AuthorID INT PRIMARY KEY, Name VARCHAR(50));
CREATE TABLE AuthorBio (AuthorID INT PRIMARY KEY, Biography TEXT, FOREIGN KEY (AuthorID) REFERENCES Author(AuthorID));

What will this query return?

SELECT Author.Name, AuthorBio.Biography FROM Author LEFT JOIN AuthorBio ON Author.AuthorID = AuthorBio.AuthorID;

AAll biographies with their authors; NULL if no author exists

BOnly authors who have biographies

CAll authors with their biographies; NULL if no biography exists

DAn error because of mismatched primary keys

Step-by-Step Solution

Solution:

Step 1: Understand LEFT JOIN
LEFT JOIN returns all rows from the left table (Author) and matching rows from the right table (AuthorBio).
Step 2: Check for missing matches
If an author has no biography, AuthorBio.Biography will be NULL.
Final Answer:
All authors with their biographies; NULL if no biography exists correctly describes the result.
Quick Check:
LEFT JOIN includes all left rows with NULLs for missing right rows [OK]

Quick Trick: LEFT JOIN returns all left rows, NULLs if no match [OK]

Common Mistakes:

MISTAKES

Confusing LEFT JOIN with INNER JOIN
Assuming only matched rows are returned
Thinking primary key mismatch causes query error

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Given these tables:

Step 1: Understand LEFT JOIN

Step 2: Check for missing matches

Final Answer:

Quick Check:

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