Cursors in Oracle PL/SQL are a crucial feature that allows you to process each row returned by a query individually. They are essentially pointers that allow you to fetch and manipulate rows of data from the database efficiently. In this blog, we will delve into the types of cursors, how to declare, open, fetch, and close them, and other essential aspects like cursor attributes and parameterized cursors.
Implicit Cursors
Implicit cursors are automatically created by Oracle whenever a DML (Data Manipulation Language) statement like INSERT, UPDATE, DELETE, or a single-row SELECT statement is executed. These cursors are managed internally by Oracle, and you do not need to explicitly declare or open them. They are ideal for simple operations where you only need to process one row at a time.
Example:
Explicit Cursors
Explicit cursors are defined by the programmer and provide more control over the context area. They are used for queries that return multiple rows, allowing you to fetch and process each row individually.
Declaring, Opening, Fetching, and Closing Cursors
Declaring: Define the cursor with the DECLARE statement. Opening: Allocate memory for the cursor and execute the SQL query using the OPEN statement. Fetching: Retrieve rows one at a time using the FETCH statement. Closing: Release the memory and resources associated with the cursor using the CLOSE statement.
Example:
Conclusion
Cursors in PL/SQL provide a powerful mechanism for row-by-row processing of query results. Understanding the differences between implicit and explicit cursors, how to declare and control them, and leveraging advanced features like parameterized cursors and FOR UPDATE can significantly enhance your ability to manage and manipulate data efficiently.
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