Oracle SQL Oracle SQL Joins and Subqueries

Question 1

Which type of JOIN returns only rows where there is a match in BOTH tables?

Accepted Answer

INNER JOIN

Answer

An INNER JOIN returns only those rows where the join condition is satisfied in both tables, excluding unmatched rows.

Question 2

What does a LEFT OUTER JOIN return in Oracle SQL?

Accepted Answer

All rows from the left table and matching rows from the right

Answer

A LEFT OUTER JOIN returns all rows from the left table and NULL for unmatched columns from the right table.

Question 3

In Oracle SQL, what is the legacy syntax equivalent of a LEFT OUTER JOIN?

Accepted Answer

table1, table2 WHERE table1.id = table2.id(+)

Answer

Oracle's proprietary (+) operator placed on the right side of the condition creates a LEFT OUTER JOIN.

Question 4

What does a CROSS JOIN produce in Oracle SQL?

Accepted Answer

A Cartesian product of all rows from both tables

Answer

A CROSS JOIN produces a Cartesian product, pairing every row from the first table with every row from the second table.

Question 5

Which Oracle SQL subquery type returns a single value used in a WHERE clause comparison?

Accepted Answer

Scalar subquery

Answer

A scalar subquery returns exactly one row and one column, making it suitable for use with single-value comparison operators like =, >, <.

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