Query By Form definition
In Query By Form (QBF) format, the columns of ONE table can be queried. In its simplest form, the field values determine the query condition:
which corresponds to this query:
Wildcards, operators, and special characters can be used to refine the query:
The following table describes the operators that can be used:
•'AND' and 'OR' are aliases for the '&' and '|' operators and can be used everywhere where these operators can be used.
•<, <=, =, > are comparison operators. These operators are followed by a value. In combination with this value they form a Boolean expression.
•A value on itself without a comparison operator is also a Boolean expression. It implicitly uses the '=' operator.
•&, |, AND, OR are logical operators. These operators are preceded and followed by a Boolean expression. With these expressions they form a new Boolean expression.
•! is a unary operator. This operator expects a Boolean expression on the right side. With this expression it forms a Boolean expression.
•() encapsulates a Boolean expression.
•In a YACC (Yet Another Compiler-Compiler) parser-like notation the definition of the syntax allowed is:
expression : VALUE
| < VALUE
| <= VALUE
| = VALUE
| > VALUE
| >= VALUE
| ! expression
| expression & expression
| expression | expression
| ( expression )
| expression AND expression
| expression OR expression