Implicit Cursors in PL/SQL

PL/SQL offers two types of cursors: 1) implicit and 2) explicit. In this lesson, we will look at implicit cursors.
PL/SQL declares and manages cursors implicitly every time you execute a SQL statement, such as a SELECT or an INSERT statement that returns only a single record. Within Oracle, the most recent implicit cursor is referred to as "SQL." Oracle opens and closes an implicit cursor automatically. You cannot open, fetch, or close an implicit cursor. However, you can use the attributes of a cursor to get information about the most recently executed implicit statement. An implicit cursor is a session cursor that is constructed and managed by PL/SQL. PL/SQL opens an implicit cursor every time you run a SELECT or DML statement. You cannot control an implicit cursor, but you can get information from its attributes. The syntax of an implicit cursor attribute value is SQLattribute (therefore, an implicit cursor is also called a SQL cursor). SQL attribute always refers to the most recently run SELECT or DML statement. If no such statement has run, the value of SQLattribute is NULL. An implicit cursor closes after its associated statement runs; however, its attribute values remain available until another SELECT or DML statement runs. The most recently run SELECT or DML statement might be in a different scope. To save an attribute value for later use, assign it to a local variable immediately. Otherwise, other operations, such as subprogram invocations, might change the value of the attribute before you can test it.

• When to use Implicit cursors:
  An implicit cursor can be used when:
  1. A single record must be processed within a SELECT statement
  2. Multiple records must be processed within a DELETE or an UPDATE statement

1. A SELECT statement must return exactly one record.
2. If the result set includes no record or more than one record, PL/SQL returns an error and passes control to the exception section of the PL/SQL block.
3. In an implicit cursor with an INSERT, UPDATE, or DELETE statement, the result set can be more than one record.

DECLARE
  pet_count NUMBER;
BEGIN
  SELECT CURRENT_INVENTORY_COUNT
    INTO pet_count 
	FROM PRODUCT
    WHERE PRODUCT_NAME = 'Canary';			 
  DBMS_OUTPUT.PUT_LINE('Number of Canary''s = ' || pet_count);
END;

1. A SELECT statement must return exactly one record.

2. DECLARE 
   pet_count NUMBER;
   

The implicit cursor attributes are:

1. SQL%ISOPEN Attribute: Is the Cursor Open?
2. SQL%FOUND Attribute: Were Any Rows Affected?
3. SQL%NOTFOUND Attribute: Were No Rows Affected?
4. SQL%ROWCOUNT Attribute: How Many Rows Were Affected?
5. SQL%BULK_ROWCOUNT
6. SQL%BULK_EXCEPTIONS

Getting Number of Rows Affected by FORALL Statement
After a FORALL statement completes, you can get the number of rows that each DML statement affected from the implicit cursor attribute SQL%BULK_ROWCOUNT. To get the total number of rows affected by the FORALL statement, use the implicit cursor attribute SQL%ROWCOUNT described in the following section.
SQL%BULK_ROWCOUNT is like an associative array whose ith element is the number of rows affected by the ith DML statement in the most recently completed FORALL statement. The data type of the element is PLS_INTEGER.
SQL%ROWCOUNT Attribute: How Many Rows Were Affected?

Cursor attributes for FORALL