USER MANUALS

Syntax Conventions

The following sections of this document describe the different operations that can be executed using VQL. The notation and syntax conventions used for this description are provided below.

  • The language is case-insensitive. I.e. “CREATE VIEW” is equivalent to “create view”.

  • <rule> Name of a grammar rule. It indicates an element whose syntax will be specified later. If the separator : appears (e.g. <name:element-definition>), this indicates a name of a representative element followed by the name of the element that defines it.

  • ::= The element to the left of the symbol is defined by the constructs on the right.

  • [...] In the definition of a rule, elements within brackets are optional.

  • The asterisk (*) indicates that an element can be specified zero or more times. Example: [ <search_method_clause> ]* indicates that the element <search_method_clause> can appear zero, one or more times.

  • The plus sign (+) indicates that an element can be specified one or more times. Example: [<field>]+ indicates that the element <field> should appear at least once and can be repeated as many times as required.

  • Elements separated by the character | and possibly grouped between braces ({}) indicate alternative elements. For example: { BASIC | <authentication> } indicates that the token BASIC or the grammar rule authentication have to occur in this position.

  • The commas (,) are used in syntax constructions to separate the elements of a list.

  • The brackets (( )) normally serve to group expressions and increase priority. In some cases, they are required as part of the specific syntax of a statement.

  • A whitespace character can be a space, a horizontal tab, or a line-feed.

  • Identifiers (<identifier>) are the names of the elements of the catalog. If at least one of the characters of the identifier is not a number or in is not in the range of “a” to “z”, it is a <quoted identifier>. Therefore, it has to be surrounded with double quotes (e.g. "identifier with space"). Certain words cannot be used as identifiers. See the definition of <reserved words> below, in Basic elements of VQL statements.

  • Numbers (<number>). A number is a combination of digits that can be preceded by the - symbol and can include a full stop as a decimal separator point and optionally an exponent (if they are real numbers).

  • Logical values (<boolean>). Representation of the true and false logical values.

  • Literals (<literal>). A literal is a sequence of characters surrounded by single quotes. A single quote has to be escaped with another single quote ('').

  • Operators (<operator>). Represent operators in the system.

Basic elements of VQL statements
<identifier> ::=
    <basic identifier>
  | <quoted identifier>

<basic identifier> ::=
  [A-Za-z][A-Za-z_0-9]*

  ; The first character of a basic identifier has to be in the ranges from "a" to "z" or from "A" to "Z".
  ; The following characters have to be in the ranges from "a" to "z", from "A" to "Z", a digit or the underscore ("_").


<quoted identifier> ::=
  ".*"

  ; Identifiers surrounded with double quotes can contain any character.
  ; A double quote within an identifier has to be escaped with another double quote. E.g. "identifier""with quote".

<view identifier> :: =
  <identifier with database>

<identifier with database> ::=
    <element:identifier> (assumes that the element exists in the current database)
  | <database:identifier>.<view:identifier>

<integer> ::=
  [-][0-9]+

<number>  ::=
    <integer>
  | (([0-9]*\.[0-9]+)|([0-9]+\.[0-9]*)) ((([0-9]*\.[0-9]+)|([0-9]+\.[0-9]*)|([0-9]+))([Ee][-+][0-9]+))

<boolean> ::=
    TRUE
  | FALSE

<literal> ::= '.*' (a single quote in a literal has to be escaped with another single quote. E.g. 'literal''with a quote')

<operator> ::=
    <unary operator>
  | <binary operator>

<operator symbol> ::=
  [~!@#^&|?<>=]+

<unary operator> ::=
    is null
  | is not null
  | is true
  | is false

<binary operator> ::=
    =
  | <identifier>
  | <operator symbol>
  | IN
Basic elements of VQL statements - reserved words
<reserved words> ::=
    ADD | ALL | ALTER | AND | ANY | AS | ASC | BASE | BOTH
  | CASE | CONNECT | CONTEXT | CREATE | CROSS | CURRENT_DATE | CURRENT_TIMESTAMP
  | CUSTOM | DATABASE | DEFAULT | DESC | DF | DISTINCT | DROP | EXISTS | FALSE
  | FETCH | FLATTEN | FROM | FULL | GRANT | GROUP BY | HASH | HAVING
  | HTML | IF | INNER | INTERSECT,INTO | IS | JDBC | JOIN | LDAP | LEADING
  | LEFT | LIMIT | LOCALTIME | LOCALTIMESTAMP | MERGE | MINUS | MY | NATURAL | NESTED | NOS | NOT | NULL
  | OBL | ODBC | OF | OFF | OFFSET | ON | ONE | OPT | OR | ORDER BY | ORDERED
  | PRIVILEGES | READ | REVERSEORDER | REVOKE | RIGHT | ROW | SELECT | SWAP
  | TABLE | TO | TRACE | TRAILING | TRUE | UNION | USER | USING | VIEW | WHEN
  | WHERE | WITH | WRITE | WS | ZERO
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