public interface Joinable
Joinable interface provides the methods for getting and
 setting a match column, which is the basis for forming the SQL JOIN
 formed by adding RowSet objects to a JoinRowSet
 object.
 
 Any standard RowSet implementation may implement
 the Joinable interface in order to be
 added to a JoinRowSet object. Implementing this interface gives
 a RowSet object the ability to use Joinable methods,
 which set, retrieve, and get information about match columns.  An
 application may add a
 RowSet object that has not implemented the Joinable
 interface to a JoinRowSet object, but to do so it must use one
 of the JoinRowSet.addRowSet methods that takes both a
 RowSet object and a match column or an array of RowSet
 objects and an array of match columns.
 
 To get access to the methods in the Joinable interface, a
 RowSet object implements at least one of the
 five standard RowSet interfaces and also implements the
 Joinable interface.  In addition, most RowSet
 objects extend the BaseRowSet class.  For example:
 
     class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {
         :
         :
     }
 
 
 The methods in the Joinable interface allow a RowSet object
 to set a match column, retrieve a match column, or unset a match column, which is
 the column upon which an SQL JOIN can be based.
 An instance of a class that implements these methods can be added to a
 JoinRowSet object to allow an SQL JOIN relationship to
  be established.
 
     CachedRowSet crs = new MyRowSetImpl();
     crs.populate((ResultSet)rs);
     (Joinable)crs.setMatchColumnIndex(1);
     JoinRowSet jrs = new JoinRowSetImpl();
     jrs.addRowSet(crs);
 
 In the previous example, crs is a CachedRowSet object that
 has implemented the Joinable interface.  In the following example,
 crs2 has not, so it must supply the match column as an argument to the
 addRowSet method. This example assumes that column 1 is the match
 column.
 
     CachedRowSet crs2 = new MyRowSetImpl();
     crs2.populate((ResultSet)rs);
     JoinRowSet jrs2 = new JoinRowSetImpl();
     jrs2.addRowSet(crs2, 1);
 
 
 The JoinRowSet interface makes it possible to get data from one or
 more RowSet objects consolidated into one table without having to incur
 the expense of creating a connection to a database. It is therefore ideally suited
 for use by disconnected RowSet objects. Nevertheless, any
 RowSet object may implement this interface
 regardless of whether it is connected or disconnected. Note that a
 JdbcRowSet object, being always connected to its data source, can
 become part of an SQL JOIN directly without having to become part
 of a JoinRowSet object.
 
setMatchColumn methods indicates
 how many match columns are being set (the length of the array) in addition to
 which columns will be used for the match. For example:
 
     int[] i = {1, 2, 4, 7}; // indicates four match columns, with column
                             // indexes 1, 2, 4, 7 participating in the JOIN.
     Joinable.setMatchColumn(i);
 
 Subsequent match columns may be added as follows to a different Joinable
 object (a RowSet object that has implemented the Joinable
 interface).
 
     int[] w = {3, 2, 5, 3};
     Joinable2.setMatchColumn(w);
 
 When an application adds two or more RowSet objects to a
 JoinRowSet object, the order of the indexes in the array is
 particularly important. Each index of
 the array maps directly to the corresponding index of the previously added
 RowSet object. If overlap or underlap occurs, the match column
 data is maintained in the event an additional Joinable RowSet is
 added and needs to relate to the match column data. Therefore, applications
 can set multiple match columns in any order, but
 this order has a direct effect on the outcome of the SQL JOIN.
 This assertion applies in exactly the same manner when column names are used rather than column indexes to indicate match columns.
JoinRowSet| Modifier and Type | Method and Description | 
|---|---|
| int[] | getMatchColumnIndexes()Retrieves the indexes of the match columns that were set for this
  RowSetobject with the methodsetMatchColumn(int[] columnIdxes). | 
| String[] | getMatchColumnNames()Retrieves the names of the match columns that were set for this
  RowSetobject with the methodsetMatchColumn(String [] columnNames). | 
| void | setMatchColumn(int columnIdx)Sets the designated column as the match column for this  RowSetobject. | 
| void | setMatchColumn(int[] columnIdxes)Sets the designated columns as the match column for this  RowSetobject. | 
| void | setMatchColumn(String columnName)Sets the designated column as the match column for this  RowSetobject. | 
| void | setMatchColumn(String[] columnNames)Sets the designated columns as the match column for this  RowSetobject. | 
| void | unsetMatchColumn(int columnIdx)Unsets the designated column as the match column for this  RowSetobject. | 
| void | unsetMatchColumn(int[] columnIdxes)Unsets the designated columns as the match column for this  RowSetobject. | 
| void | unsetMatchColumn(String columnName)Unsets the designated column as the match column for this  RowSetobject. | 
| void | unsetMatchColumn(String[] columnName)Unsets the designated columns as the match columns for this  RowSetobject. | 
void setMatchColumn(int columnIdx)
             throws SQLException
RowSet
 object. A JoinRowSet object can now add this RowSet
 object based on the match column.
 
 Sub-interfaces such as the CachedRowSet™
 interface define the method CachedRowSet.setKeyColumns, which allows
 primary key semantics to be enforced on specific columns.
 Implementations of the setMatchColumn(int columnIdx) method
 should ensure that the constraints on the key columns are maintained when
 a CachedRowSet object sets a primary key column as a match column.
columnIdx - an int identifying the index of the column to be
        set as the match columnSQLException - if an invalid column index is setsetMatchColumn(int[]), 
unsetMatchColumn(int)void setMatchColumn(int[] columnIdxes)
             throws SQLException
RowSet
 object. A JoinRowSet object can now add this RowSet
 object based on the match column.columnIdxes - an array of int identifying the indexes of the
      columns to be set as the match columnsSQLException - if an invalid column index is setsetMatchColumn(int[]), 
unsetMatchColumn(int[])void setMatchColumn(String columnName) throws SQLException
RowSet
 object. A JoinRowSet object can now add this RowSet
 object based on the match column.
 
 Subinterfaces such as the CachedRowSet interface define
 the method CachedRowSet.setKeyColumns, which allows
 primary key semantics to be enforced on specific columns.
 Implementations of the setMatchColumn(String columnIdx) method
 should ensure that the constraints on the key columns are maintained when
 a CachedRowSet object sets a primary key column as a match column.
columnName - a String object giving the name of the column
      to be set as the match columnSQLException - if an invalid column name is set, the column name
      is a null, or the column name is an empty stringunsetMatchColumn(int), 
setMatchColumn(int[])void setMatchColumn(String[] columnNames) throws SQLException
RowSet
 object. A JoinRowSet object can now add this RowSet
 object based on the match column.columnNames - an array of String objects giving the names
     of the column to be set as the match columnsSQLException - if an invalid column name is set, the column name
      is a null, or the column name is an empty stringunsetMatchColumn(int), 
setMatchColumn(int[])int[] getMatchColumnIndexes()
                     throws SQLException
RowSet object with the method
 setMatchColumn(int[] columnIdxes).int array identifying the indexes of the columns
         that were set as the match columns for this RowSet objectSQLException - if no match column has been setsetMatchColumn(int), 
unsetMatchColumn(int)String[] getMatchColumnNames() throws SQLException
RowSet object with the method
 setMatchColumn(String [] columnNames).String objects giving the names of the columns
         set as the match columns for this RowSet objectSQLException - if no match column has been setsetMatchColumn(int), 
unsetMatchColumn(int)void unsetMatchColumn(int columnIdx)
               throws SQLException
RowSet
 object.
 
 RowSet objects that implement the Joinable interface
 must ensure that a key-like constraint continues to be enforced until the
 method CachedRowSet.unsetKeyColumns has been called on the
 designated column.
columnIdx - an int that identifies the index of the column
          that is to be unset as a match columnSQLException - if an invalid column index is designated or if
          the designated column was not previously set as a match
          columnsetMatchColumn(int)void unsetMatchColumn(int[] columnIdxes)
               throws SQLException
RowSet
 object.columnIdxes - an array of int that identifies the indexes
     of the columns that are to be unset as match columnsSQLException - if an invalid column index is designated or if
          the designated column was not previously set as a match
          columnsetMatchColumn(int)void unsetMatchColumn(String columnName) throws SQLException
RowSet
 object.
 
 RowSet objects that implement the Joinable interface
 must ensure that a key-like constraint continues to be enforced until the
 method CachedRowSet.unsetKeyColumns has been called on the
 designated column.
columnName - a String object giving the name of the column
          that is to be unset as a match columnSQLException - if an invalid column name is designated or
          the designated column was not previously set as a match
          columnsetMatchColumn(int)void unsetMatchColumn(String[] columnName) throws SQLException
RowSet
 object.columnName - an array of String objects giving the names of
     the columns that are to be unset as the match columnsSQLException - if an invalid column name is designated or the
     designated column was not previously set as a match columnsetMatchColumn(int) Submit a bug or feature 
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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