What
are Cursors?
- A cursor is a temporary work area created in the system memory
when a SQL statement is executed. A cursor contains information on a select
statement and the rows of data accessed by it. This temporary work area is used
to store the data retrieved from the database, and manipulate this data. A
cursor can hold more than one row, but can process only one row at a time. The
set of rows the cursor holds is called theactive set.
There are two types of cursors in PL/SQL:
Implicit cursors:
- These are created by default when DML statements like, INSERT, UPDATE, and DELETE statements are executed. They are also created when a SELECT statement that returns just one row is executed.
Explicit cursors:
- They must be created when you are executing a SELECT statement that returns more than one row. Even though the cursor stores multiple records, only one record can be processed at a time, which is called as current row. When you fetch a row the current row position moves to next row.
Both implicit and explicit
cursors have the same functionality, but they differ in the way they are
accessed.
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