2.5. Operators and Special Characters

A set of special characters is reserved for use as operators or separators.

  |<special char> ::=
  |    <space> | " | % | & | ' | ( | ) | * | + | , | -
  |  | . | / | : | ; | < | = | > | ? | [ | ] | ^ | { | }

Some of these characters, alone or in combinations, may be used as operators (arithmetical, string, logical), as SQL command separators, to quote identifiers and to mark the limits of string literals or comments.

Operator Syntax 

   |<operator> ::=
   |    <string concatenation operator>
   |  | <arithmetic operator>
   |  | <comparison operator>
   |  | <logical operator>
   | 
   |<string concatentation operator> ::= "||"
   | 
   |<arithmetic operator> ::= * | / | + | - |
   | 
   |<comparison operator> ::=
   |    =  | <> | != | ~= | ^= | > | < | >= | <=
   |  | !> | ~> | ^> | !< | ~< | ^<
   | 
   |<logical operator> ::= NOT | AND | OR

For more details on operators, see Expressions.