Package nz.co.gregs.dbvolution.expressions.windows

Class WindowFunctionRequiresOrderBy<A extends EqualExpression<?,?,?>>

java.lang.Object

nz.co.gregs.dbvolution.expressions.windows.WindowFunctionRequiresOrderBy<A>

Type Parameters:

A - the expression type returned by this windowing function, e.g. IntegerExpression

All Implemented Interfaces:

DBExpression, HasSQLString, WindowingFunctionRequiresOrderByInterface<A>

Direct Known Subclasses:

StringExpression.LagLeadWindow

public class WindowFunctionRequiresOrderBy<A extends EqualExpression<?,?,?>>
extends Object
implements WindowingFunctionRequiresOrderByInterface<A>

Author:

gregorygraham

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	WindowFunctionRequiresOrderBy.Partitioned<A extends EqualExpression<?,?,?>>
static class	WindowFunctionRequiresOrderBy.Sorted<A extends EqualExpression<?,?,?>>

Nested classes/interfaces inherited from interface nz.co.gregs.dbvolution.expressions.windows.WindowingFunctionRequiresOrderByInterface

WindowingFunctionRequiresOrderByInterface.WindowEnd<A extends EqualExpression<?,?,?>>, WindowingFunctionRequiresOrderByInterface.WindowPart<A extends EqualExpression<?,?,?>>

Constructor Summary

Constructors

Constructor	Description
WindowFunctionRequiresOrderBy(A expression)

Method Summary

Modifier and Type	Method	Description
WindowFunctionRequiresOrderBy.Partitioned<A>	allRows()
A	AllRowsAndOrderBy(SortProvider sort, SortProvider... sorts)
WindowFunctionRequiresOrderBy<A>	copy()	A Complete Copy Of This DBValue.
String	createSQLForFromClause(DBDatabase database)
String	createSQLForGroupByClause(DBDatabase database)
A	getInnerExpression()
QueryableDatatype<?>	getQueryableDatatypeForExpressionValue()	Provides a blank instance of the QueryableDatatype used by this expression.
Class<A>	getRequiredExpressionClass()
Set<DBRow>	getTablesInvolved()	Returns a Set of the DBRow instances involved in this expression.
boolean	isAggregator()	Returns TRUE if this expression is an Aggregator like SUM() or LEAST().
boolean	isComplexExpression()
boolean	isPurelyFunctional()	Indicates whether or not the expression includes table columns.
boolean	isWindowingFunction()
WindowFunctionRequiresOrderBy.Partitioned<A>	partition(ColumnProvider... cols)
String	toSQLString(DBDefinition defn)	Produces the snippet provided by this class.
WindowFunctionRequiresOrderBy.Partitioned<A>	unpartitioned()

Methods inherited from class java.lang.Object

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

Constructor Detail

WindowFunctionRequiresOrderBy

public WindowFunctionRequiresOrderBy(A expression)

Method Detail

partition

public WindowFunctionRequiresOrderBy.Partitioned<A> partition(ColumnProvider... cols)

Specified by:

partition in interface WindowingFunctionRequiresOrderByInterface<A extends EqualExpression<?,?,?>>

getInnerExpression

public A getInnerExpression()

AllRowsAndOrderBy

public A AllRowsAndOrderBy(SortProvider sort,
                           SortProvider... sorts)

toSQLString

public String toSQLString(DBDefinition defn)

Description copied from interface: HasSQLString

Produces the snippet provided by this class.

This is only used internally.

If you are extending DBvolution and adding a new function this is the place to format the information for use in SQL. A DBDefinition instance is provided to supply context and so your SQL can used on multiple database engines.

Specified by:

toSQLString in interface HasSQLString

Parameters:

defn - the target database

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Returns:

the DBValue formatted as a SQL snippet

getRequiredExpressionClass

public Class<A> getRequiredExpressionClass()

Specified by:

getRequiredExpressionClass in interface WindowingFunctionRequiresOrderByInterface<A extends EqualExpression<?,?,?>>

copy

public WindowFunctionRequiresOrderBy<A> copy()

Description copied from interface: DBExpression

A Complete Copy Of This DBValue.

Immutability in DBvolution is maintain by internally copying objects.

This method enables immutability by performing a deep copy of the object.

Singletons may return themselves but all other objects must return a new instance with copies of all mutable fields.

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Specified by:

copy in interface DBExpression

Returns:

a copy of this DBValue

getQueryableDatatypeForExpressionValue

public QueryableDatatype<?> getQueryableDatatypeForExpressionValue()

Description copied from interface: DBExpression

Provides a blank instance of the QueryableDatatype used by this expression.

You are probably looking for ExpressionColumn.asExpressionColumn().

Note that this method is not good for use in everyday DBvolution code and should probably be reserved for meta-programming.

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Specified by:

getQueryableDatatypeForExpressionValue in interface DBExpression

Returns:

the QueryableDatatype subclass that corresponds to the results of this expression

isAggregator

public boolean isAggregator()

Description copied from interface: DBExpression

Returns TRUE if this expression is an Aggregator like SUM() or LEAST().

Subclasses must implement this method returning TRUE if the expression will combine the results of several rows to produce a result. If the expression relies on subexpressions, then the isAggregator method must return TRUE if the subexpressions include an aggregator.

Aggregators collect several rows together to produce a single result. Examples are MAX, MIN, and AVERAGE.

They are only appropriate in the SELECT clause and generally require the GROUP BY clause to be useful.

Aggregators are used with DBReport. Aggregator expressions are included in the SELECT clause but excluded from the GROUP BY clause.

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Specified by:

isAggregator in interface DBExpression

Returns:

TRUE if this DBExpression represents an aggregating functions

getTablesInvolved

public Set<DBRow> getTablesInvolved()

Description copied from interface: DBExpression

Returns a Set of the DBRow instances involved in this expression.

Used by QueryGraph to plot the connections between tables and avoid cartesian joins.

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Specified by:

getTablesInvolved in interface DBExpression

Returns:

a set of DBRow instances involved in this DBExpression.

isPurelyFunctional

public boolean isPurelyFunctional()

Description copied from interface: DBExpression

Indicates whether or not the expression includes table columns.

Purely functional expressions use only in-built functions or literal values to produce results and do not require data from tables.

Some databases, notably MS SQLServer, can not group purely functional expressions.

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Specified by:

isPurelyFunctional in interface DBExpression

Returns:

TRUE if the expression does not access table data, otherwise FALSE.

isComplexExpression

public boolean isComplexExpression()

Specified by:

isComplexExpression in interface DBExpression

createSQLForFromClause

public String createSQLForFromClause(DBDatabase database)

Specified by:

createSQLForFromClause in interface DBExpression

createSQLForGroupByClause

public String createSQLForGroupByClause(DBDatabase database)

Specified by:

createSQLForGroupByClause in interface DBExpression

isWindowingFunction

public boolean isWindowingFunction()

Specified by:

isWindowingFunction in interface DBExpression

unpartitioned

public WindowFunctionRequiresOrderBy.Partitioned<A> unpartitioned()

allRows

public WindowFunctionRequiresOrderBy.Partitioned<A> allRows()