Microsoft SQL Server Development for Everyone - Left, Right, and Full Join

The video tutorial covers SQL join operations, focusing on inner, left, right, and full joins. It begins with a review of design decisions for the enrollments table, highlighting the importance of foreign key values. The tutorial then explains how inner joins work, followed by a detailed look at left joins, which return all records from the left table. Right joins are discussed next, showing how they return all records from the right table. Finally, full joins are introduced, which combine the results of left and right joins, returning all records from both tables.

Why might an enrollment exist without a teacher assigned?

• The student has not been assigned a course.

• A teacher has not been assigned yet.

• The enrollment is invalid.

• The course is not yet created.

What is the primary condition for an inner join to return a row?

• The row must exist in both tables.

• The row must have a null value.

• The row must be unique.

• The row must be in the left table only.

How does a left join differ from an inner join?

• It returns only matching rows from both tables.

• It returns all rows from the left table, regardless of matches.

• It only returns rows from the right table.

• It returns all rows from both tables.

In a left join, what happens if there is no matching data on the right?

• The row is omitted.

• The row is duplicated.

• The row is returned with nulls for the right table columns.

• The row is returned with default values.

What is the main focus of a right join?

• To return all rows from the left table.

• To return rows with null values only.

• To return only matching rows from both tables.

• To return all rows from the right table.

In a right join, what happens to rows in the left table without a match?

• They are duplicated.

• They are returned with nulls for the left table columns.

• They are returned with default values.

• They are omitted.

What does a full join return?

• Only matching rows from both tables.

• All rows from both tables, with nulls where there are no matches.

• All rows from the left table only.

• All rows from the right table only.

How does a full join handle non-matching rows?

• It duplicates them.

• It returns them with nulls for the missing side.

• It omits them.

• It returns them with default values.

Which join type would you use to ensure all records from both tables are included?

• Inner join

• Left join

• Full join

• Right join

What is the key difference between left and right joins?

• Left join returns only matching rows, right join returns all rows.

• Left join focuses on the right table, right join on the left.

• Left join returns all rows from the left table, right join from the right.

• Left join returns all rows, right join returns none.