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Discover the key differences between `explicit` and `implicit` cursors in Oracle PL/SQL. Learn when to use each type and how they impact your database operations.
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Understanding the Difference Between Explicit and Implicit Cursors in Oracle

As a developer working with Oracle PL/SQL, you're likely to encounter both explicit and implicit cursors. However, if you've been away from your cursor knowledge for a while, you may find yourself asking, what's the difference between these two types of cursors? In this guide, we will clarify this distinction, discussing what each cursor type is, how they work, and when to use them. Let’s dive in!

What is a Cursor?

Before we delve into the differences, let's briefly understand what a cursor is. In Oracle, a cursor is a database object that allows you to retrieve and manipulate rows returned by a query. However, there are two types of cursors: explicit and implicit.

Implicit Cursors

What is an Implicit Cursor?

An implicit cursor is automatically created by Oracle whenever you execute a SQL statement that returns results. This type of cursor is simple to use and requires less coding on your part. However, be cautious as implicit cursors have their drawbacks.

Drawbacks of Implicit Cursors

Inefficiency: The ANSI standard dictates that implicit cursors must fetch results twice. This can lead to slower performance, especially with large data sets.

Vulnerability to Data Errors: If your query returns multiple rows, an implicit cursor will raise a TOO_MANY_ROWS exception, which could disrupt your application flow.

Example of an Implicit Cursor

Here’s a brief example of how an implicit cursor works in practice:

[[See Video to Reveal this Text or Code Snippet]]

In this example, Oracle handles the cursor management for you. However, it’s also essential to be aware of its limitations.

Explicit Cursors

What is an Explicit Cursor?

An explicit cursor, on the other hand, is one you create and manage manually. This approach provides greater control over your data retrieval process, but it also requires more code and understanding of PL/SQL.

Advantages of Explicit Cursors

Control: You can manage rows more flexibly. For instance, you can open a cursor, fetch just what you need, and close it without worrying about how many tables might return results.

Error Handling: With explicit cursors, you can handle the NO_DATA_FOUND and TOO_MANY_ROWS exceptions more effectively to ensure your application behaves as expected.

Example of an Explicit Cursor

To illustrate how an explicit cursor operates, consider the following example:

[[See Video to Reveal this Text or Code Snippet]]

In this snippet, you have complete control over how the information is retrieved and processed.

When to Use Which Cursor?

Choosing between implicit and explicit cursors largely depends on your specific use case:

Use Implicit Cursors When:

You have a simple query that returns a single row.

You want less code and are confident about the returned results.

Use Explicit Cursors When:

Your queries are complex and return multiple rows.

You need robust error handling and control over the fetched data.

Conclusion

Understanding the differences between explicit and implicit cursors in Oracle is crucial for efficient database programming. While implicit cursors provide simplicity, explicit cursors offer you the control necessary to handle more complex operations. As you navigate between these options, consider the specific needs of your application to make the best choice.

By mastering the use of cursors, you'll be able to optimize your database operations and write cleaner, more efficient PL/SQL code.