You can declare variables using DECLARE block or statement.

Note that you can mix both syntaxes in a single program. DECLARE blocks and statements can appear in any part of the program.

DECLARE block has the following syntax:

DECLARE 
  var datatype [NOT NULL] [:= | = | DEFAULT expression];
  ...
BEGIN
  ...
END;

HPL/SQL also allows you to define a constant:

  var CONSTANT datatype := | DEFAULT expression

Example:

DECLARE
  code CHAR(10);
  status INT := 1;
  count SMALLINT = 0;
  limit INT DEFAULT 100;  
  max_limit CONSTANT INT := 1000;
BEGIN 
  ...
END;

Compatibility: Declaration block syntax is similar to Oracle PL/SQL, PostgreSQL PL/pgSQL and Netezza NZPLSQL.

DECLARE statement has the following syntax:

DECLARE var [, var2, ...] [AS] datatype [:= | = | DEFAULT expression] [, ...];

Example:

DECLARE code CHAR(10);
DECLARE status, status2 INT DEFAULT 1;
DECLARE count SMALLINT, limit INT DEFAULT 100;  

Compatibility: Declaration statement syntax is similar to IBM DB2 SQL PL, Teradata, Microsoft SQL Server Transact-SQL and MySQL.