Declare Variables, Constants and Types in Oracle PL/SQL

You declare PL/SQL variables, constants and types in declare block. The syntax is

     <name> [CONSTANT] <datatype> [NOT NULL] [:= | DEFAULT <expr>]

• <name> is the name of the variable or constant;
• <datatype> may be scalar, composite datatype, reference or LOB;
• <expr> is a literal value, another variable or any PL/SQL expression. The result of the expression is used to assign the default value of the variable or constant.

• If you are defining a constant, you must provide the value of the constant in the definition.
• TABLE, RECORD, NESTED TABLE and VARRAY are composite types.
• To define scalar type you can refer to [schema.]object%TYPE or cursor%TYPE.
• For record type you can refer to [schema.]object%ROWTYPE.

Examples:

DECLARE
  --Define some scalar variables
  v_year NUMBER(4);
  v_pin VARCHAR2(12);
  v_min_amount NUMBER(20, 2) := 25000;
 
  --Define a record type
  TYPE t_customer IS RECORD (
    id NUMBER(18),
    first_name VARCHAR2(32),
    last_name VARCHAR2(32),
  );
  --Declare a record variable
  v_customer t_customer;
 
  --Declare a composite type to hold a list of records
  TYPE t_customer_list IS TABLE OF t_customer;
 
  --Declare a record variable refering an existing table
  v_employee employee%ROWTYPE;
BEGIN
   v_year := 2010;
   -- More PL/SQL code here.
END;

Declare RECORD variables and types

A specific RECORD TYPE corresponding to a fixed number (and datatype) of underlying table columns can simplify the job of defining variables.

%TYPE is used to declare a field with the same type as that of a specified table’s column.
%ROWTYPE is used to declare a record with the same types as found in the specified database table, view or cursor.

Declare RECORD type

TYPE <type_name> IS RECORD(
    <field_declaration>,...);

Each record field is declared with its ‘field_declaration’:

   <field_name> {<field_type> |
               <variable>%TYPE |
               <table.column>%TYPE |
               <table>%ROWTYPE}
               [ [NOT NULL] {:= | DEFAULT} <expr> ]

The <field_type> can be any PL/SQL data type except REF CURSOR.

To declare a record variable:

   <variable_identifier> <type_name>;

You can declare a variable based on a record reference using %ROWTYPE:

   <variable_name> <table_or_curosr_name>%ROWTYPE

The number of variables and their data type is evaluated at run-time.