DECLARE customer char(30); fiscal_year number(2) := '97'; You can use the symbol := to initialize, or assign an initial value, to variables in the DECLARE...

You must initialize a variable that is defined as NOT NULL.
DECLARE
customer char(30);
fiscal_year number(2) NOT NULL := '97';
ANALYSIS:
The NOT NULL clause in the definition of fiscal_year resembles a column definition in a CREATE TABLE statement.
Constant Assignment
Constants are defined the same way that variables are, but constant values are static;
they do not change. In the previous example, fiscal_year is probably a constant.
NOTE: You must end each variable declaration with a semicolon.
Cursor Definitions
A cursor is another type of variable in PL/SQL. Usually when you think of a variable, a
single value comes to mind. A cursor is a variable that points to a row of data from the results of a query. In a multiple-row result set, you need a way to scroll through each
record to analyze the data. A cursor is just that. When the PL/SQL block looks at the
results of a query within the block, it uses a cursor to point to each returned row. Here is an example of a cursor being defined in a PL/SQL block:
INPUT:
DECLARE
cursor employee_cursor is
select * from employees;
A cursor is similar to a view. With the use of a loop in the PROCEDURE section, you can scroll a cursor. This technique is covered shortly.
The %TYPE Attribute
%TYPE is a variable attribute that returns the value of a given column of a table.
Instead of hard-coding the data type in your PL/SQL block, you can use %TYPE to
maintain data type consistency within your blocks of code.
INPUT:
DECLARE
cursor employee_cursor is
select emp_id, emp_name from employees;
id_num employees.emp_id%TYPE;
name employees.emp_name%TYPE;
ANALYSIS:
The variable id_num is declared to have the same data type as emp_id in the EMPLOYEES
table. %TYPE declares the variable name to have the same data type as the column emp_name in the EMPLOYEES table.
The %ROWTYPE Attribute
Variables are not limited to single values. If you declare a variable that is associated
with a defined cursor, you can use the %ROWTYPE attribute to declare the data type of that variable to be the same as each column in one entire row of data from the cursor.
In Oracle's lexicon the %ROWTYPE attribute creates a record variable.
INPUT:
DECLARE
cursor employee_cursor is
select emp_id, emp_name from employees;
employee_record employee_cursor%ROWTYPE;
ANALYSIS:
This example declares a variable called employee_record. The %ROWTYPE attribute defines this variable as having the same data type as an entire row of data in the
employee_cursor. Variables declared using the %ROWTYPE attribute are also called aggregate variables.
The %ROWCOUNT Attribute
The PL/SQL %ROWCOUNT attribute maintains a count of rows that the SQL statements in the particular block have accessed in a cursor.
INPUT:
DECLARE
cursor employee_cursor is
select emp_id, emp_name from employees;
records_processed := employee_cursor%ROWCOUNT;
ANALYSIS:
In this example the variable records_processed represents the current number of rows that the PL/SQL block has accessed in the employee_cursor.
WARNING: Beware of naming conflicts with table names when declaring
variables. For instance, if you declare a variable that has the same name as
a table that you are trying to access with the PL/SQL code, the local
variable will take precedence over the table name.
The PROCEDURE Section
The PROCEDURE section is the only mandatory part of a PL/SQL block. This part of the
block calls variables and uses cursors to manipulate data in the database. The PROCEDURE section is the main part of a block, containing conditional statements and SQL commands.
BEGIN...END
In a block, the BEGIN statement denotes the beginning of a procedure. Similarly, the END
statement marks the end of a procedure. The following example shows the basic
structure of the PROCEDURE section:
SYNTAX:
BEGIN
open a cursor;
condition1;
statement1;
condition2;
statement2;
condition3;
statement3;
.
.
.
close the cursor;
END
Cursor Control Commands