Lecture 3-Cusors and Records.pdf - Cursors and Records 1...

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Cursors and Records 1
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Oracle creates a memory area, known as context area, for processing an SQL statement. It contains all information needed for processing the statement, for example, number of rows processed, etc. A cursor is a pointer to this context area. PL/SQL controls the context area through a cursor. A cursor holds the rows (one or more) returned by a SQL statement. The set of rows the cursor holds is referred to as the active set . 2
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Two types: Implicit cursors Explicit cursors Implicit cursors are automatically created by Oracle whenever an SQL statement is executed. Whenever a DML statement (INSERT, UPDATE and DELETE) is issued, an implicit cursor is associated with this statement. For INSERT operations, the cursor holds the data that needs to be inserted. For UPDATE and DELETE operations, the cursor identifies the rows that would be affected. 3
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In PL/SQL, you can refer to the most recent implicit cursor as the SQL cursor. It always has the attributes like %FOUND, %ISOPEN, %NOTFOUND, and %ROWCOUNT. The SQL cursor has additional attributes, %BULK_ROWCOUNT and %BULK_EXCEPTIONS, designed for use with the FORALL statement. 4
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Attribute Description %FOUND Returns TRUE if an INSERT, UPDATE, or DELETE statement affected one or more rows or a SELECT INTO statement returned one or more rows. Otherwise, it returns FALSE. %NOTFOUND The logical opposite of %FOUND. It returns TRUE if an INSERT, UPDATE, or DELETE statement affected no rows, or a SELECT INTO statement returned no rows. Otherwise, it
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