/*******************************************************************************
* Copyright (c) 2006, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation
*
******************************************************************************/
package org.eclipse.persistence.jpa.jpql.parser;
/**
* A role describes the purpose of the JPQL identifier.
*
* @version 2.5
* @since 2.3
* @author Pascal Filion
*/
public enum IdentifierRole {
/**
* Indicates the identifier aggregates two expressions together. The identifiers are <b>AND</b>,
* <b>OR</b>, and the arithmetic operators.
*/
AGGREGATE,
/**
* Indicates the identifier is used to create a clause. They are the root of a portion of the
* query. An example is <b>SELECT</b>.
*/
CLAUSE,
/**
* Indicates the identifier is used to complement an expression, it is not required for creating
* an expression. Examples are <b>AS</b> or <b>OUTER</b>.
*/
COMPLEMENT,
/**
* Indicates the identifier is a kind of function, it does not return a value but it is used to
* perform some operation over an expression. The expression can have an expression before and
* after but it's not used to aggregate those two expression. An example is <b>x MEMBER y</b>.
*/
COMPOUND_FUNCTION,
/**
* Indicates the identifier is used to create a function, it has some parameters and returns a
* value. An example is <b>ABS(x)</b>, usually the identifier has some values encapsulated with
* parenthesis.
* <p>
* Note: <b>TRUE</b>, <b>FALSE</b>, <b>NULL</b>, <b>CURRENT_DATE</b>, <b>CURRENT_TIME</b>,
* <b>CURRENT_TIMESTAMP</b> are considered functions.
*/
FUNCTION,
/**
* Indicates the identifier is not part of the language but it has been reserved for future use.
* The identifiers are <b>BIT_LENGTH</b>, <b>CHAR_LENGTH</b>, <b>CHARACTER_LENGTH</b>,
* <b>POSITION</b>, and <b>UNKNOWN</b>.
*/
UNUSED
}