In PL/SQL, what is a cursor and what are the main types of cursors that developers use to process query result sets?

Introduction / Context:
When working with SQL inside PL/SQL, queries can return multiple rows. PL/SQL uses cursors to process these result sets row by row. Cursors provide a controlled way to fetch, examine, and manipulate rows. This question asks you to define what a cursor is and to identify the main types of cursors that PL/SQL offers to developers.

Given Data / Assumptions:

• The language in question is PL/SQL, commonly used with Oracle Database.
• SQL queries may return zero, one, or many rows.
• We want to understand how PL/SQL interacts with multi row result sets.
• We assume basic knowledge of SELECT statements and control structures.

Concept / Approach:
A cursor in PL/SQL is a pointer or handle to the context area that stores the result set of a query. It allows PL/SQL code to fetch rows one at a time and process them. PL/SQL provides implicit cursors, which are created automatically for simple SQL statements, and explicit cursors, which are declared and managed by the programmer. Explicit cursors give more control over open, fetch, and close operations, and can be parameterized. There are also cursor variables and ref cursors, but the core classification is implicit versus explicit.

Step-by-Step Solution:
1. Recognize that executing a query in PL/SQL causes the database to allocate a context area containing the result set. 2. Understand that a cursor is a name or handle that PL/SQL uses to interact with this context area. 3. Recall that for simple DML and SELECT statements, PL/SQL uses implicit cursors, such as SQL, without explicit declarations. 4. Note that developers can declare explicit cursors to process query results with fine grained control, including loops and parameters. 5. Choose the option that correctly describes a cursor as a handle to a query result set and names implicit and explicit as the main types.

Verification / Alternative check:
You can verify by writing a simple PL/SQL block that executes a SELECT into statement and then checks attributes of the implicit cursor, such as SQL%ROWCOUNT. Then write another block that declares an explicit cursor, opens it, fetches rows in a loop, and closes it. Both examples demonstrate that cursors provide access to result sets, and they illustrate the difference between automatic and manual cursor management.

Why Other Options Are Wrong:

• Option B is wrong because cursors are not temporary tables stored in client browsers; they are server side constructs tied to queries.
• Option C is wrong because cursors are not triggers; triggers are separate PL/SQL units that respond to DML events.
• Option D is wrong because cursors do not store database version information; that is unrelated metadata.

Common Pitfalls:
Common mistakes include forgetting to close explicit cursors, which can lead to resource leaks, and misusing implicit cursor attributes when multiple statements are executed in the same block. Developers may also fetch beyond the end of a result set if they do not check for cursor exhaustion correctly. Understanding how cursors map to context areas and how implicit and explicit cursors behave helps you write efficient, correct PL/SQL code that processes rows safely.

Final Answer:
The correct explanation is A cursor is a handle to a query result set, and PL/SQL supports implicit cursors managed automatically and explicit cursors defined and controlled by the programmer, because this captures both the definition of a cursor and the main cursor types used in PL/SQL programming.