org.axiondb.functions

Class NullIfFunction

java.lang.Object

org.axiondb.BaseSelectable

org.axiondb.functions.BaseFunction

org.axiondb.functions.NullIfFunction

All Implemented Interfaces:

java.io.Serializable, Function, FunctionFactory, ConcreteFunction, ScalarFunction, Selectable

public class NullIfFunction
extends BaseFunction
implements ScalarFunction, FunctionFactory

The NULLIF function returns a null value if the arguments are equal, otherwise it returns the value of the first argument.

The result of using NULLIF(e1,e2) is the same as using the expression CASE WHEN e1=e2 THEN NULL ELSE e1 END

Version:

$Revision: 1.5 $ $Date: 2005/12/20 18:32:28 $

See Also:

Serialized Form

Field Summary

Fields inherited from class org.axiondb.BaseSelectable

_hash

Constructor Summary

Constructors

Constructor and Description
NullIfFunction()

Method Summary

Modifier and Type	Method and Description
java.lang.Object	evaluate(RowDecorator row)
DataType	getDataType() AnyType
boolean	isValid()
ConcreteFunction	makeNewInstance()

Methods inherited from class org.axiondb.functions.BaseFunction

addArgument, getArgument, getArgumentCount, setArgument, setVariableContext, toString

Methods inherited from class org.axiondb.BaseSelectable

getAlias, getLabel, getName, setAlias, setName

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.axiondb.Function

addArgument, getAlias, getArgument, getArgumentCount, getName, setAlias, setArgument

Methods inherited from interface org.axiondb.Selectable

getLabel, setVariableContext

Constructor Detail

NullIfFunction

public NullIfFunction()

Method Detail

makeNewInstance

public ConcreteFunction makeNewInstance()

Specified by:

makeNewInstance in interface FunctionFactory

getDataType

public DataType getDataType()

AnyType

Specified by:

getDataType in interface Selectable

Specified by:

getDataType in class BaseFunction

evaluate

public java.lang.Object evaluate(RowDecorator row)
                          throws AxionException

Specified by:

evaluate in interface ScalarFunction

Specified by:

evaluate in interface Selectable

Throws:

AxionException

isValid

public boolean isValid()

Specified by:

isValid in interface ConcreteFunction

Specified by:

isValid in class BaseFunction