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Questions and Answers
What is the primary advantage of using a cursor FOR LOOP compared to traditional cursor management?
What is the primary advantage of using a cursor FOR LOOP compared to traditional cursor management?
- It handles the closing of the cursor automatically. (correct)
- It automatically opens the cursor for you. (correct)
- It allows multiple cursors to be used simultaneously.
- It eliminates the need to check for cursor errors.
In a cursor FOR LOOP, what does the 'record' variable represent?
In a cursor FOR LOOP, what does the 'record' variable represent?
- A temporary storage for loop control variables.
- An index used for external references outside the loop.
- The implicit cursor variable representing a row from the cursor. (correct)
- A summary of all processed records.
Which of the following statements is true regarding the 'cursor_name' in a cursor FOR LOOP?
Which of the following statements is true regarding the 'cursor_name' in a cursor FOR LOOP?
- The cursor can be referenced outside the loop after execution.
- The cursor can be a SELECT statement or an explicit cursor. (correct)
- The cursor must be explicitly opened before using it in the loop.
- It can only be used for SELECT operations from a single table.
What happens when there are no more rows to fetch in a cursor FOR LOOP?
What happens when there are no more rows to fetch in a cursor FOR LOOP?
How is the record variable scoped within a cursor FOR LOOP?
How is the record variable scoped within a cursor FOR LOOP?
In the cursor example provided, what output would be generated if there are no customers in the database?
In the cursor example provided, what output would be generated if there are no customers in the database?
What is the purpose of the EXIT statement in the context of a cursor FETCH operation?
What is the purpose of the EXIT statement in the context of a cursor FETCH operation?
Which of the following correctly describes the syntax of a cursor FOR LOOP?
Which of the following correctly describes the syntax of a cursor FOR LOOP?
What does the cursor FOR LOOP automatically manage that traditional cursor management does not?
What does the cursor FOR LOOP automatically manage that traditional cursor management does not?
What implication does the local scope of the 'record' variable have in a cursor FOR LOOP?
What implication does the local scope of the 'record' variable have in a cursor FOR LOOP?
In the syntax of a cursor FOR LOOP, what is meant by 'process_record_statements'?
In the syntax of a cursor FOR LOOP, what is meant by 'process_record_statements'?
What is required for a cursor to work in a cursor FOR LOOP?
What is required for a cursor to work in a cursor FOR LOOP?
What happens to the cursor when the cursor FOR LOOP completes execution?
What happens to the cursor when the cursor FOR LOOP completes execution?
When using the syntax 'FOR record IN (select_statement)', what type of data does 'record' contain?
When using the syntax 'FOR record IN (select_statement)', what type of data does 'record' contain?
How does the cursor FOR LOOP differ in its execution cycle from traditional cursor management?
How does the cursor FOR LOOP differ in its execution cycle from traditional cursor management?
What type of variable is implicitly created by the cursor FOR LOOP for each iteration?
What type of variable is implicitly created by the cursor FOR LOOP for each iteration?
Flashcards
Cursor FOR LOOP
Cursor FOR LOOP
A loop construct in PL/SQL that automatically handles the opening, fetching, and closing of a cursor, simplifying the process of iterating through a result set.
Record Variable (in Cursor FOR LOOP)
Record Variable (in Cursor FOR LOOP)
A PL/SQL variable that is implicitly created within a cursor FOR loop to store each row fetched from the cursor. It has the same structure as the cursor's row type.
Cursor Name (in Cursor FOR LOOP)
Cursor Name (in Cursor FOR LOOP)
The name of the cursor that the cursor FOR loop uses to fetch and process data. It can be either an explicitly declared cursor or a SELECT statement.
SELECT Statement (as Cursor Name)
SELECT Statement (as Cursor Name)
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Cursor
Cursor
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Explicit Cursor (in PL/SQL)
Explicit Cursor (in PL/SQL)
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Cursor %NOTFOUND (in PL/SQL)
Cursor %NOTFOUND (in PL/SQL)
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DBMS_OUTPUT.PUT_LINE
DBMS_OUTPUT.PUT_LINE
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Study Notes
PL/SQL Cursor FOR LOOP
- Implicit Cursor Handling: The
FORloop simplifies cursor operations by implicitly handlingOPEN,FETCH, andCLOSEstatements. - Record Variable: The loop automatically creates a record variable (
%ROWTYPE) to hold the fetched data, streamlining row access. This record variable is local to the loop. - Efficient Data Access: It fetches data row by row, eliminating the need for manual loop index management.
- Automatic Cursor Closure: If no more rows are available, the cursor is automatically closed.
- Loop Index as Record: The loop implicitly creates a loop index as a
%ROWTYPErecord variable that matches the cursor's result set. - Direct Fetch: In each iteration, the
FORloop fetches a row into the loop index. - No Manual Management: The
FORloop eliminates manual control over the cursor's execution cycle (OPEN, FETCH, CLOSE).
Cursor FOR LOOP Syntax
FOR record IN cursor_name LOOP: This structure uses a pre-defined cursor.FOR record IN (select_statement) LOOP: Alternatively, aSELECTstatement can be used directly within the loop's definition.
Example Usage
- Fetching Customer Data: Illustrates retrieving data from the
customerstable using a cursor loop. This example displays customer ID, name, and address. - Customer Data Display: Shows how to display customer information.
Important Considerations
- Record Scope: The record variable is local to the
FORloop and is not accessible outside its scope. - Cursor Name: The
cursor_namerefers to a declared cursor object. The cursor is not opened when the loop starts. - Select Statement: A
SELECTstatement can be placed directly within theFORloop definition to define the data source.
Another Example
- Finding Mass-Priced Products: This example fetches product names and list prices within a specified price range, using a named cursor (
c_product). - Looping and Displaying Data: Iterates through the products, displaying the product name and price.
- Explicitly Defined Cursor: This example uses a declared cursor (
c_product), demonstrating its usage with aSELECTstatement.
Example Code Snippets (Demonstrating implicit cursor)
- Customer Data Example:
CURSOR c_customers IS
SELECT id, name, address FROM customers;
BEGIN
OPEN c_customers;
FOR customer_record IN c_customers LOOP
DBMS_OUTPUT.PUT_LINE(customer_record.id || ' ' || customer_record.name || ' ' || customer_record.address);
END LOOP;
CLOSE c_customers;
END;
/
- Mass Product Example:
CURSOR c_product(low_price IN NUMBER, high_price IN NUMBER) IS
SELECT product_name, list_price
FROM products
WHERE list_price BETWEEN low_price AND high_price;
BEGIN
- - show mass products
DBMS_OUTPUT.PUT_LINE('Mass products: ');
FOR product_record IN c_product(50, 100) LOOP
DBMS_OUTPUT.PUT_LINE(product_record.product_name || ': ' || product_record.list_price);
END LOOP;
END;
/
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