Declarative Objectivity (DO) Language : Data Clauses : WHERE Clause
WHERE Clause
A WHERE clause qualifies the objects to be operated on by a RETURN, UPDATE, or DELETE statement.
Syntax 
whereClause : WHERE expression;
Used In 
RETURN Statement, UPDATE Statement, DELETE Statement
Quick Look 
Return the seating capacity of a vehicle whose license is XLT5663:
FROM Vehicles WHERE license == 'XLT5663' RETURN model.seatingCapacity;
Return the last name of the customer(s) whose rentals include a contract with the tracking number 122.
FROM Customers WHERE ANY(rentals, trackingNumber == 122) RETURN lastName;
Discussion 
A WHERE clause defines a subset of the query source to be returned or modified in a RETURN, UPDATE, or DELETE statement.
The clause’s expression specifies the condition(s) that must be met by qualified objects in the query source. The expression must be a predicate expression, which is an expression that returns a Boolean value. The predicate expression is tested against each source object and its values, and evaluates to true if the object meets the specified condition, or to false if the condition is not met. Any source object for which the predicate returns true is passed along to the next clause.