org.apache.empire.db.expr.join

Class DBJoinExpr

java.lang.Object

org.apache.empire.db.DBObject

org.apache.empire.db.DBExpr

org.apache.empire.db.expr.join.DBJoinExpr

All Implemented Interfaces:

DBPreparable

Direct Known Subclasses:

DBColumnJoinExpr, DBCrossJoinExpr

public abstract class DBJoinExpr
extends DBExpr
implements DBPreparable

This class is used for building a join expression of an SQL statement. There is no need to explicitly create instances of this class.

Field Summary

Fields

Modifier and Type	Field and Description
protected DBJoinType	type

Fields inherited from class org.apache.empire.db.DBExpr

CTX_ALIAS, CTX_ALL, CTX_DEFAULT, CTX_FULLNAME, CTX_NAME, CTX_NOPARENTHESIS, CTX_VALUE

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	DBJoinExpr(DBJoinType type) Constructs a new DBJoinExpr object initialize this object with the left and right column and the data type of the join expression.

Method Summary

Modifier and Type	Method and Description
abstract DBJoinExpr	copy(DBCommand newCmd) Copy Command
abstract DBRowSet	getLeftTable() returns the RowSet on the left of the join
abstract DBRowSet	getOuterTable() Returns the left table name if the data type= JOIN_LEFT and returns the right table if the data type= JOIN_RIGHT.
abstract DBRowSet	getRightTable() returns the RowSet on the right of the join
DBJoinType	getType() returns the join type for this join
abstract boolean	isJoinOn(DBColumn column) returns true if this join is using the given column or false otherwise
abstract boolean	isJoinOn(DBRowSet rowset) returns true if this join is using the given table or view or false otherwise
abstract void	reverse() This function swaps the left and the right statements of the join expression.
void	setType(DBJoinType type) alters the join type for this join

Methods inherited from class org.apache.empire.db.DBExpr

addReferencedColumns, addSQL

Methods inherited from class org.apache.empire.db.DBObject

checkParamNull, getDatabase

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.empire.db.expr.column.DBPreparable

prepareParams

Field Detail

type

protected DBJoinType type

Constructor Detail

DBJoinExpr

protected DBJoinExpr(DBJoinType type)

Constructs a new DBJoinExpr object initialize this object with the left and right column and the data type of the join expression.

Parameters:

type - the join type (JOIN_INNER, JOIN_LEFT or JOIN_RIGHT)

Method Detail

getType

public DBJoinType getType()

returns the join type for this join

Returns:

the join type

setType

public void setType(DBJoinType type)

alters the join type for this join

Parameters:

type - the join type

getLeftTable

public abstract DBRowSet getLeftTable()

returns the RowSet on the left of the join

Returns:

the rowset on the left

getRightTable

public abstract DBRowSet getRightTable()

returns the RowSet on the right of the join

Returns:

the rowset on the right

isJoinOn

public abstract boolean isJoinOn(DBRowSet rowset)

returns true if this join is using the given table or view or false otherwise

Parameters:

rowset - the rowset to check

Returns:

true if the join is on the given rowset

isJoinOn

public abstract boolean isJoinOn(DBColumn column)

returns true if this join is using the given column or false otherwise

Parameters:

column - the column to check

Returns:

true if the join is on the given column

getOuterTable

public abstract DBRowSet getOuterTable()

Returns the left table name if the data type= JOIN_LEFT and returns the right table if the data type= JOIN_RIGHT. If the data type = JOIN_INNER the return value is null.

Returns:

the current DBDatabase object

reverse

public abstract void reverse()

This function swaps the left and the right statements of the join expression.

copy

public abstract DBJoinExpr copy(DBCommand newCmd)

Copy Command

Parameters:

newCmd - the new command object

Returns:

the join expression