Difference between Implicit and Explicit Cursors

In databases, cursors are essential tools that allow developers to retrieve and manipulate data row by row. Cursors provide a mechanism to process each record in a query result individually and making them useful when working with complex data sets.

Cursors can be categorized into two types Implicit Cursors and Explicit Cursors. In this article, we will learn the difference between Implicit Cursors and Explicit Cursors.

What are Implicit Cursors?

An implicit cursor is a simple tool in databases that works automatically in the background. Imagine it as an invisible pointer that moves through the data for us. When we run a command to fetch information, the implicit cursor automatically processes the data one step at a time, starting from the beginning and going to the end. we don’t need to set it up or manage it yourself; it does all the work for us.

This makes it easier for beginners because you don’t have to worry about handling the cursor. The database takes care of it, so we can focus on getting the information we need.

Advantages of Implicit Cursors

1. Automatic Handling: Implicit cursors are automatically created and managed by the database. This makes it simpler for beginners, as there is no need to explicitly declare, open, fetch, or close them.
2. Less Code: Since they work automatically, they require less code, reducing the risk of coding errors.
3. Efficient for Simple Queries: Ideal for executing simple SQL statements like SELECT INTO, as there is no need for complex cursor management.
4. Less Maintenance: The system manages implicit cursors, freeing the user from managing resources like opening, fetching, and closing the cursor.

Disadvantages of Implicit Cursors

1. Limited Control: Implicit cursors provide limited control over the data fetching process. You cannot control when to open, fetch, or close the cursor, or perform operations like skipping rows or repositioning.
2. Fetches Single Row: Implicit cursors can only handle single-row operations. If multiple rows are expected, they may lead to errors.
3. Error-Prone for Complex Queries: Since implicit cursors are automatically managed, they can sometimes lead to errors, such as when multiple rows are returned but only one is expected.
4. Less Efficient for Complex Operations: Implicit cursors are less efficient for complex queries that need more programmatic control, making them unsuitable for large-scale data handling.

What is Explicit Cursors?

An explicit cursor is a database tool that we control directly. Imagine it as a pointer that moves through data one step at a time, and we decide when it starts, moves, and stops. With explicit cursors, we can specify what data to look at and how to handle it. we can go through the data row by row, skip some rows, or go back if needed and giving us a more control over the process.

Even though explicit cursors take more effort to set up and use than implicit cursors, they are very helpful for handling more complex tasks. They might seem a bit tricky at first, especially for beginners, but they are very useful for managing detailed and advanced data operations.

Advantages of Explicit Cursors

1. Greater Control: Explicit cursors give complete control over the cursor operations like opening, fetching, and closing the cursor. You can process each row of a result set one by one.
2. Multiple Row Handling: Explicit cursors can handle multiple rows, making them more versatile for complex queries and large datasets.
3. Flexibility: You can use explicit cursors to perform various operations like skipping rows, rolling back to previous rows, or manipulating data based on complex conditions.
4. Error Handling: You have more control over error handling since you can check the cursor's status after each fetch and handle errors more gracefully.

Disadvantages of Explicit Cursors

1. More Code: Explicit cursors require more code to declare, open, fetch, and close, which increases the complexity of the program.
2. Manual Management: You are responsible for managing the cursor’s lifecycle, which includes proper opening, fetching, and closing. Forgetting to close the cursor can lead to memory leaks.
3. Higher Maintenance: Since you need to manage the cursor manually, it increases the chances of errors, especially in complex programs.
4. Increased Complexity: Beginners may find it difficult to use explicit cursors initially due to the complexity involved in handling multiple rows and cursor attributes.

Difference between Implicit and Explicit Cursors

Conclusion

The Implicit cursors work automatically in the background doing the job for you without needing the input. They are easy to use but dont give much control. Explicit cursors are like the tools you control yourself. You decide how to use them and which gives you more power but also means more work. Implicit cursors are great for the simple tasks while explicit the cursors are better for more complex jobs where you need the precise control over the data. Beginners mostly start with the implicit cursors because they are easier and then learn to use the explicit cursors as they tackle more advanced databases tasks.