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JavaTM 2 Platform Standard Ed. 5.0 |
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public interface JoinRowSet
The JoinRowSet interface provides a mechanism for combining related
data from different RowSet objects into one JoinRowSet
object, which represents an SQL JOIN.
In other words, a JoinRowSet object acts as a
container for the data from RowSet objects that form an SQL
JOIN relationship.
The Joinable interface provides the methods for setting,
retrieving, and unsetting a match column, the basis for
establishing an SQL JOIN relationship. The match column may
alternatively be set by supplying it to the appropriate version of the
JointRowSet method addRowSet.
RowSet objects (CachedRowSet objects
and implementations extending the CachedRowSet interface)
do not have a standard way to establish an SQL JOIN between
RowSet objects without the expensive operation of
reconnecting to the data source. The JoinRowSet
interface is specifically designed to address this need.
Any RowSet object
can be added to a JoinRowSet object to become
part of an SQL JOIN relationship. This means that both connected
and disconnected RowSet objects can be part of a JOIN.
RowSet objects operating in a connected environment
(JdbcRowSet objects) are
encouraged to use the database to which they are already
connected to establish SQL JOIN relationships between
tables directly. However, it is possible for a
JdbcRowSet object to be added to a JoinRowSet object
if necessary.
Any number of RowSet objects can be added to an
instance of JoinRowSet provided that they
can be related in an SQL JOIN.
By definition, the SQL JOIN statement is used to
combine the data contained in two or more relational database tables based
upon a common attribute. The Joinable interface provides the methods
for establishing a common attribute, which is done by setting a
match column. The match column commonly coincides with
the primary key, but there is
no requirement that the match column be the same as the primary key.
By establishing and then enforcing column matches,
a JoinRowSet object establishes JOIN relationships
between RowSet objects without the assistance of an available
relational database.
The type of JOIN to be established is determined by setting
one of the JoinRowSet constants using the method
setJoinType. The following SQL JOIN types can be set:
CROSS_JOIN
FULL_JOIN
INNER_JOIN - the default if no JOIN type has been set
LEFT_OUTER_JOIN
RIGHT_OUTER_JOIN
JOIN will automatically be an
inner join. The comments for the fields in the
JoinRowSet interface explain these JOIN types, which are
standard SQL JOIN types.
JoinRowSet Object for Creating a JOINJoinRowSet object is created, it is empty.
The first RowSet object to be added becomes the basis for the
JOIN relationship.
Applications must determine which column in each of the
RowSet objects to be added to the JoinRowSet object
should be the match column. All of the
RowSet objects must contain a match column, and the values in
each match column must be ones that can be compared to values in the other match
columns. The columns do not have to have the same name, though they often do,
and they do not have to store the exact same data type as long as the data types
can be compared.
A match column can be be set in two ways:
Joinable method setMatchColumnRowSet
object is added to a JoinRowSet object. The RowSet object
must have implemented the Joinable interface in order to use the method
setMatchColumn. Once the match column value
has been set, this method can be used to reset the match column at any time.
JoinRowSet method
addRowSet that takes a column name or number (or an array of
column names or numbers)addRowSet methods take a match column as a parameter.
These four methods set or reset the match column at the time a RowSet
object is being added to a JoinRowSet object.
The following code fragment adds two CachedRowSet
objects to a JoinRowSet object. Note that in this example,
no SQL JOIN type is set, so the default JOIN type,
which is INNER_JOIN, is established.
In the following code fragment, the table EMPLOYEES, whose match
column is set to the first column (EMP_ID), is added to the
JoinRowSet object jrs. Then
the table ESSP_BONUS_PLAN, whose match column is likewise
the EMP_ID column, is added. When this second
table is added to jrs, only the rows in
ESSP_BONUS_PLAN whose EMP_ID value matches an
EMP_ID value in the EMPLOYEES table are added.
In this case, everyone in the bonus plan is an employee, so all of the rows
in the table ESSP_BONUS_PLAN are added to the JoinRowSet
object. In this example, both CachedRowSet objects being added
have implemented the Joinable interface and can therefore call
the Joinable method setMatchColumn.
JoinRowSet jrs = new JoinRowSetImpl();
ResultSet rs1 = stmt.executeQuery("SELECT * FROM EMPLOYEES");
CachedRowSet empl = new CachedRowSetImpl();
empl.populate(rs1);
empl.setMatchColumn(1);
jrs.addRowSet(empl);
ResultSet rs2 = stmt.executeQuery("SELECT * FROM ESSP_BONUS_PLAN");
CachedRowSet bonus = new CachedRowSetImpl();
bonus.populate(rs2);
bonus.setMatchColumn(1); // EMP_ID is the first column
jrs.addRowSet(bonus);
At this point, jrs is an inside JOIN of the two RowSet objects
based on their EMP_ID columns. The application can now browse the
combined data as if it were browsing one single RowSet object.
Because jrs is itself a RowSet object, an application can
navigate or modify it using RowSet methods.
jrs.first();
int employeeID = jrs.getInt(1);
String employeeName = jrs.getString(2);
Note that because the SQL JOIN must be enforced when an application
adds a second or subsequent RowSet object, there
may be an initial degradation in performance while the JOIN is
being performed.
The following code fragment adds an additional CachedRowSet object.
In this case, the match column (EMP_ID) is set when the
CachedRowSet object is added to the JoinRowSet object.
ResultSet rs3 = stmt.executeQuery("SELECT * FROM 401K_CONTRIB");
CachedRowSet fourO1k = new CachedRowSetImpl();
four01k.populate(rs3);
jrs.addRowSet(four01k, 1);
The JoinRowSet object jrs now contains values from all three
tables. The data in each row in four01k in which the value for the
EMP_ID column matches a value for the EMP_ID column
in jrs has been added to jrs.
JoinRowSet MethodsJoinRowSet interface supplies several methods for adding
RowSet objects and for getting information about the
JoinRowSet object.
RowSet objectsRowSet object
at a time or to add multiple RowSet objects at one time. In
either case, the methods may specify the match column for each
RowSet object being added.
RowSet objects in the
JoinRowSet object, and another method retrieves the
RowSet names. A third method retrieves either the SQL
WHERE clause used behind the scenes to form the
JOIN or a text description of what the WHERE
clause does.
JOINJOIN type, and five methods find out whether
the JoinRowSet object supports a given type.
JoinRowSet object
| Field Summary | |
|---|---|
static int |
CROSS_JOIN
An ANSI-style JOIN providing a cross product of two tables |
static int |
FULL_JOIN
An ANSI-style JOIN providing a a full JOIN. |
static int |
INNER_JOIN
An ANSI-style JOIN providing a inner join between two tables. |
static int |
LEFT_OUTER_JOIN
An ANSI-style JOIN providing a left outer join between two
tables. |
static int |
RIGHT_OUTER_JOIN
An ANSI-style JOIN providing a right outer join between
two tables. |
| Fields inherited from interface javax.sql.rowset.WebRowSet |
|---|
PUBLIC_XML_SCHEMA, SCHEMA_SYSTEM_ID |
| Fields inherited from interface javax.sql.rowset.CachedRowSet |
|---|
COMMIT_ON_ACCEPT_CHANGES |
| Fields inherited from interface java.sql.ResultSet |
|---|
CLOSE_CURSORS_AT_COMMIT, CONCUR_READ_ONLY, CONCUR_UPDATABLE, FETCH_FORWARD, FETCH_REVERSE, FETCH_UNKNOWN, HOLD_CURSORS_OVER_COMMIT, TYPE_FORWARD_ONLY, TYPE_SCROLL_INSENSITIVE, TYPE_SCROLL_SENSITIVE |
| Method Summary | |
|---|---|
void |
addRowSet(Joinable rowset)
Adds the given RowSet object to this JoinRowSet
object. |
void |
addRowSet(RowSet[] rowset,
int[] columnIdx)
Adds one or more RowSet objects contained in the given
array of RowSet objects to this JoinRowSet
object and sets the match column for
each of the RowSet objects to the match columns
in the given array of column indexes. |
void |
addRowSet(RowSet[] rowset,
String[] columnName)
Adds one or more RowSet objects contained in the given
array of RowSet objects to this JoinRowSet
object and sets the match column for
each of the RowSet objects to the match columns
in the given array of column names. |
void |
addRowSet(RowSet rowset,
int columnIdx)
Adds the given RowSet object to this JoinRowSet
object and sets the designated column as the match column for
the RowSet object. |
void |
addRowSet(RowSet rowset,
String columnName)
Adds rowset to this JoinRowSet object and
sets the designated column as the match column. |
int |
getJoinType()
Returns a int describing the set SQL JOIN type
governing this JoinRowSet instance. |
String[] |
getRowSetNames()
Returns a String array containing the names of the
RowSet objects added to this JoinRowSet
object. |
Collection<?> |
getRowSets()
Returns a Collection object containing the
RowSet objects that have been added to this
JoinRowSet object. |
String |
getWhereClause()
Return a SQL-like description of the WHERE clause being used in a JoinRowSet object. |
void |
setJoinType(int joinType)
Allow the application to adjust the type of JOIN imposed
on tables contained within the JoinRowSet object instance. |
boolean |
supportsCrossJoin()
Indicates if CROSS_JOIN is supported by a JoinRowSet implementation |
boolean |
supportsFullJoin()
Indicates if FULL_JOIN is supported by a JoinRowSet implementation |
boolean |
supportsInnerJoin()
Indicates if INNER_JOIN is supported by a JoinRowSet implementation |
boolean |
supportsLeftOuterJoin()
Indicates if LEFT_OUTER_JOIN is supported by a JoinRowSet implementation |
boolean |
supportsRightOuterJoin()
Indicates if RIGHT_OUTER_JOIN is supported by a JoinRowSet implementation |
CachedRowSet |
toCachedRowSet()
Creates a new CachedRowSet object containing the
data in this JoinRowSet object, which can be saved
to a data source using the SyncProvider object for
the CachedRowSet object. |
| Methods inherited from interface javax.sql.rowset.WebRowSet |
|---|
readXml, readXml, writeXml, writeXml, writeXml, writeXml |
| Methods inherited from interface javax.sql.rowset.CachedRowSet |
|---|
acceptChanges, acceptChanges, columnUpdated, columnUpdated, commit, createCopy, createCopyNoConstraints, createCopySchema, createShared, execute, getKeyColumns, getOriginal, getOriginalRow, getPageSize, getRowSetWarnings, getShowDeleted, getSyncProvider, getTableName, nextPage, populate, populate, previousPage, release, restoreOriginal, rollback, rollback, rowSetPopulated, setKeyColumns, setMetaData, setOriginalRow, setPageSize, setShowDeleted, setSyncProvider, setTableName, size, toCollection, toCollection, toCollection, undoDelete, undoInsert, undoUpdate |
| Methods inherited from interface javax.sql.rowset.Joinable |
|---|
getMatchColumnIndexes, getMatchColumnNames, setMatchColumn, setMatchColumn, setMatchColumn, setMatchColumn, unsetMatchColumn, unsetMatchColumn, unsetMatchColumn, unsetMatchColumn |
| Field Detail |
|---|
static final int CROSS_JOIN
JOIN providing a cross product of two tables
static final int INNER_JOIN
JOIN providing a inner join between two tables. Any
unmatched rows in either table of the join should be discarded.
static final int LEFT_OUTER_JOIN
JOIN providing a left outer join between two
tables. In SQL, this is described where all records should be
returned from the left side of the JOIN statement.
static final int RIGHT_OUTER_JOIN
JOIN providing a right outer join between
two tables. In SQL, this is described where all records from the
table on the right side of the JOIN statement even if the table
on the left has no matching record.
static final int FULL_JOIN
JOIN providing a a full JOIN. Specifies that all
rows from either table be returned regardless of matching
records on the other table.
| Method Detail |
|---|
void addRowSet(Joinable rowset)
throws SQLException
RowSet object to this JoinRowSet
object. If the RowSet object
is the first to be added to this JoinRowSet
object, it forms the basis of the JOIN relationship to be
established.
This method should be used only when the given RowSet
object already has a match column that was set with the Joinable
method setMatchColumn.
Note: A Joinable object is any RowSet object
that has implemented the Joinable interface.
rowset - the RowSet object that is to be added to this
JoinRowSet object; it must implement the
Joinable interface and have a match column set
SQLException - if (1) an empty rowset is added to the to this
JoinRowSet object, (2) a match column has not been
set for rowset, or (3) rowset
violates the active JOINJoinable.setMatchColumn(int)
void addRowSet(RowSet rowset,
int columnIdx)
throws SQLException
RowSet object to this JoinRowSet
object and sets the designated column as the match column for
the RowSet object. If the RowSet object
is the first to be added to this JoinRowSet
object, it forms the basis of the JOIN relationship to be
established.
This method should be used when RowSet does not already have a match column set.
rowset - the RowSet object that is to be added to this
JoinRowSet object; it may implement the
Joinable interfacecolumnIdx - an int that identifies the column to become the
match column
SQLException - if (1) rowset is an empty rowset or
(2) rowset violates the active JOINJoinable.unsetMatchColumn(int)
void addRowSet(RowSet rowset,
String columnName)
throws SQLException
JoinRowSet object and
sets the designated column as the match column. If rowset
is the first to be added to this JoinRowSet
object, it forms the basis for the JOIN relationship to be
established.
This method should be used when the given RowSet object
does not already have a match column.
rowset - the RowSet object that is to be added to this
JoinRowSet object; it may implement the
Joinable interfacecolumnName - the String object giving the name of the
column to be set as the match column
SQLException - if (1) rowset is an empty rowset or
(2) the match column for rowset does not satisfy the
conditions of the JOIN
void addRowSet(RowSet[] rowset,
int[] columnIdx)
throws SQLException
RowSet objects contained in the given
array of RowSet objects to this JoinRowSet
object and sets the match column for
each of the RowSet objects to the match columns
in the given array of column indexes. The first element in
columnIdx is set as the match column for the first
RowSet object in rowset, the second element of
columnIdx is set as the match column for the second element
in rowset, and so on.
The first RowSet object added to this JoinRowSet
object forms the basis for the JOIN relationship.
This method should be used when the given RowSet object
does not already have a match column.
rowset - an array of one or more RowSet objects
to be added to the JOIN; it may implement the
Joinable interfacecolumnIdx - an array of int values indicating the index(es)
of the columns to be set as the match columns for the RowSet
objects in rowset
SQLException - if (1) an empty rowset is added to this
JoinRowSet object, (2) a match column is not set
for a RowSet object in rowset, or (3)
a RowSet object being added violates the active
JOIN
void addRowSet(RowSet[] rowset,
String[] columnName)
throws SQLException
RowSet objects contained in the given
array of RowSet objects to this JoinRowSet
object and sets the match column for
each of the RowSet objects to the match columns
in the given array of column names. The first element in
columnName is set as the match column for the first
RowSet object in rowset, the second element of
columnName is set as the match column for the second element
in rowset, and so on.
The first RowSet object added to this JoinRowSet
object forms the basis for the JOIN relationship.
This method should be used when the given RowSet object(s)
does not already have a match column.
rowset - an array of one or more RowSet objects
to be added to the JOIN; it may implement the
Joinable interfacecolumnName - an array of String values indicating the
names of the columns to be set as the match columns for the
RowSet objects in rowset
SQLException - if (1) an empty rowset is added to this
JoinRowSet object, (2) a match column is not set
for a RowSet object in rowset, or (3)
a RowSet object being added violates the active
JOIN
Collection<?> getRowSets()
throws SQLException
Collection object containing the
RowSet objects that have been added to this
JoinRowSet object.
This should return the 'n' number of RowSet contained
within the JOIN and maintain any updates that have occured while in
this union.
Collection object consisting of the
RowSet objects added to this JoinRowSet
object
SQLException - if an error occurs generating the
Collection object to be returned
String[] getRowSetNames()
throws SQLException
String array containing the names of the
RowSet objects added to this JoinRowSet
object.
String array of the names of the
RowSet objects in this JoinRowSet
object
SQLException - if an error occurs retrieving the names of
the RowSet objectsCachedRowSet.setTableName(java.lang.String)
CachedRowSet toCachedRowSet()
throws SQLException
CachedRowSet object containing the
data in this JoinRowSet object, which can be saved
to a data source using the SyncProvider object for
the CachedRowSet object.
If any updates or modifications have been applied to the JoinRowSet
the CachedRowSet returned by the method will not be able to persist
it's changes back to the originating rows and tables in the
in the datasource. The CachedRowSet instance returned should not
contain modification data and it should clear all properties of
it's originating SQL statement. An application should reset the
SQL statement using the RowSet.setCommand method.
In order to allow changes to be persisted back to the datasource
to the originating tables, the acceptChanges method
should be used and called on a JoinRowSet object instance. Implementations
can leverage the internal data and update tracking in their
implementations to interact with the SyncProvider to persist any
changes.
SQLException - if an error occurs assembling the CachedRowSet
objectRowSet,
CachedRowSet,
SyncProviderboolean supportsCrossJoin()
boolean supportsInnerJoin()
boolean supportsLeftOuterJoin()
boolean supportsRightOuterJoin()
boolean supportsFullJoin()
void setJoinType(int joinType)
throws SQLException
JOIN imposed
on tables contained within the JoinRowSet object instance.
Implementations should throw a SQLException if they do
not support a given JOIN type.
joinType - the standard JoinRowSet.XXX static field definition
of a SQL JOIN to re-configure a JoinRowSet instance on
the fly.
SQLException - if an unsupported JOIN type is setgetJoinType()
String getWhereClause()
throws SQLException
JOIN by supplying a SQL
strings description of JOIN or provide a textual
description to assist applications using a JoinRowSet
SQLException - if an error occurs in generating a representation
of the WHERE clause.
int getJoinType()
throws SQLException
int describing the set SQL JOIN type
governing this JoinRowSet instance. The returned type will be one of
standard JoinRowSet types: CROSS_JOIN, INNER_JOIN,
LEFT_OUTER_JOIN, RIGHT_OUTER_JOIN or
FULL_JOIN.
JOIN. JoinRowSet.INNER_JOIN
is returned as the default JOIN type is no type has been
explicitly set.
SQLException - if an error occurs determining the SQL JOIN
type supported by the JoinRowSet instance.setJoinType(int)
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JavaTM 2 Platform Standard Ed. 5.0 |
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Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.