6 SQL Operators and Statements

Usage Notes

The EVALUATE operator can be used in the WHERE claus e of a SQL statement. When an Expression Filter index is defined on a column storing expressions, the EVALUATE operator on such column may use the index for the expression set evaluation based on its usage cost. The EVALUATE operator can be used as a join predicate between a table storing expressions and a table storing the corresponding data items.

If the values of all elementary attributes in the attribute set can be represented as readable values, such as those stored in VARCHAR , DATE, and NUMBER datatypes and the constructors formatted as a string, then the data item can be formatte d as a string of attribute name-value pairs. If a data item does not require a constructor for any of its elementary attribute values , then a list of values provided for the data item can be formatted as a string of name-value pairs using two getVarchar methods (a S TATIC method and a MEMBER method) in the object type associated with the attribute set.

Any data item can be formatted using a n AnyData instance. An attribute set with one or more binary typed attributes must use the AnyData form of the data item .

See "Applying the SQL EVALUATE Operator" for more information about the EVALUA TE operator.

Related views: USER_EXPFIL_ATTRIBUTE_SETS, USER_EXPFIL_ATTRIBUTES, and USER_EXPFIL_EXPRESSION_SETS

Examples

T he following query uses the VARCHAR form of the data item generated by the getVarchar() function:

SELECT * FROM Consumer WHERE 
    EVALUATE (Consumer.Interest,
               Car4Sale('Mustang',
           2000,
                         18000,
                         22000).getVarchar()
               ) = 1;

For th e previous query, the data item can be passed in the AnyData form with the following syntax:

SELECT * FROM Consumer WHERE
    EVALUATE (Consumer.Interest,
              AnyData.convertObject (
                      Car4Sale
 ('Mustang',
                                 2000,
                                 18000,
                                 22000)
             )) = 1;

When a large set of data items are stored in a table, the table storing expressions can be joined wit h the table storing data items with the following syntax:

SELECT i.CarId, c.CId, c.Phone
FROM Consumer
c, Inventory i
WHERE
     EVALUATE (c.Interest,
               Car4Sale(i.Model, i.Year, i.Price, i.Mileage).getVarchar()) = 1
ORDER
BY i.CarId;