OQL Grammar

The OQL grammar can be described as following using the BNF syntax:

query ::= select-query [UNION query]
select-query ::= SELECT class-reference [class-joined] [WHERE expression]
class-reference ::= name [AS name]
class-joined ::= JOIN class-reference ON name.name = name.id
name ::= string | `string`
expression ::=
scalar
| expression operator expression
| (expression)
scalar ::= number | ‘string’ | “string” | column
operator ::= AND | OR | = | <> | != | > | >= | < | <= | LIKE | NOT LIKE
column ::= name | name.name