An identifier is a sequence of one or more characters. The first character must be a valid first character (letter, $, _) in an identifier of the Java programming language, hereafter in this chapter called simply “Java”. Each subsequent character in the sequence must be a valid nonfirst character (letter, digit, $, _) in a Java identifier. (For details, see the Java SE API documentation of the isJavaIdentifierStart and isJavaIdentifierPart methods of the Character class.) The question mark (?) is a reserved character in the query language and cannot be used in an identifier.
A query language identifier is case-sensitive, with two exceptions:
Keywords
Identification variables
An identifier cannot be the same as a query language keyword. Here is a list of query language keywords:
ABS |
ALL |
AND |
ANY |
AS |
ASC |
AVG |
BETWEEN |
BIT_LENGTH |
BOTH |
BY |
CASE |
CHAR_LENGTH |
CHARACTER_LENGTH |
CLASS |
COALESCE |
CONCAT |
COUNT |
CURRENT_DATE |
CURRENT_TIMESTAMP |
DELETE |
DESC |
DISTINCT |
ELSE |
EMPTY |
END |
ENTRY |
ESCAPE |
EXISTS |
FALSE |
FETCH |
FROM |
GROUP |
HAVING |
IN |
INDEX |
INNER |
IS |
JOIN |
KEY |
LEADING |
LEFT |
LENGTH |
LIKE |
LOCATE |
LOWER |
MAX |
MEMBER |
MIN |
MOD |
NEW |
NOT |
NULL |
NULLIF |
OBJECT |
OF |
OR |
ORDER |
OUTER |
POSITION |
SELECT |
SET |
SIZE |
SOME |
SQRT |
SUBSTRING |
SUM |
THEN |
TRAILING |
TRIM |
TRUE |
TYPE |
UNKNOWN |
UPDATE |
UPPER |
VALUE |
WHEN |
WHERE |
It is not recommended that you use an SQL keyword as an identifier, because the list of keywords may expand to include other reserved SQL words in the future.