uk.ac.ed.epcc.webapp.jdbc.expr

Class CountDistinctExpression<T>

java.lang.Object

uk.ac.ed.epcc.webapp.jdbc.expr.CountDistinctExpression<T>

Type Parameters:

T - type of nested expression

All Implemented Interfaces:

GroupingSQLValue<java.lang.Integer>, SQLExpression<java.lang.Integer>, SQLValue<java.lang.Integer>, Targetted<java.lang.Integer>

public class CountDistinctExpression<T>
extends java.lang.Object
implements SQLExpression<java.lang.Integer>

SQLExpression that counts distinct values of an expression.

Constructor Summary

Constructors

Constructor and Description
CountDistinctExpression(SQLValue<T> expr)

Method Summary

Modifier and Type	Method and Description
int	add(java.lang.StringBuilder sb, boolean qualify) Add the expression to a StringBuilder
java.util.List<PatternArgument>	getParameters(java.util.List<PatternArgument> list) Add parameters for this value to a list.
SQLFilter	getRequiredFilter() Get an SQLFilter required to be added to the filter set.
java.lang.Class<java.lang.Integer>	getTarget() Get the type of the returned object as far as it is known.
java.lang.Integer	makeObject(java.sql.ResultSet rs, int pos) Extract a result of the expression from a ResultSet into an object of the specified type.

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.ed.epcc.webapp.jdbc.expr.SQLExpression

equals, groupingIsomorphic, hashCode

Methods inherited from interface uk.ac.ed.epcc.webapp.jdbc.expr.GroupingSQLValue

addGroup, checkContentsCanGroup, getGroupParameters

Constructor Detail

CountDistinctExpression

public CountDistinctExpression(SQLValue<T> expr)

Method Detail

add

public int add(java.lang.StringBuilder sb,
               boolean qualify)

Description copied from interface: SQLValue

Add the expression to a StringBuilder

Specified by:

add in interface SQLValue<java.lang.Integer>

Parameters:

sb - StringBuilder to modify

qualify - boolean should fields be qualified with the table name

Returns:

number of fields added

getParameters

public java.util.List<PatternArgument> getParameters(java.util.List<PatternArgument> list)

Description copied from interface: SQLValue

Add parameters for this value to a list.

Specified by:

getParameters in interface SQLValue<java.lang.Integer>

Parameters:

list - to modify

Returns:

modified list of parameter objects

makeObject

public java.lang.Integer makeObject(java.sql.ResultSet rs,
                                    int pos)
                             throws DataException,
                                    java.sql.SQLException

Description copied from interface: SQLValue

Extract a result of the expression from a ResultSet into an object of the specified type. Note that this method is also used to extract the result of functions over the result type.

Specified by:

makeObject in interface SQLValue<java.lang.Integer>

Parameters:

rs - ResultSet

Returns:

produced object

Throws:

DataException

java.sql.SQLException

getRequiredFilter

public SQLFilter getRequiredFilter()

Description copied from interface: SQLValue

Get an SQLFilter required to be added to the filter set. This is usually to implement a join.

Specified by:

getRequiredFilter in interface SQLValue<java.lang.Integer>

Returns:

null or SQLFilter

getTarget

public java.lang.Class<java.lang.Integer> getTarget()

Description copied from interface: Targetted

Get the type of the returned object as far as it is known. Normally this should be the erasure type corresponding to T.

Specified by:

getTarget in interface Targetted<java.lang.Integer>

Returns:

Class object for return type