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292 lines
12 KiB
292 lines
12 KiB
/*
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.sql.rowset;
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import java.sql.SQLException;
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/**
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* <h3>1.0 Background</h3>
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* The <code>Joinable</code> interface provides the methods for getting and
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* setting a match column, which is the basis for forming the SQL <code>JOIN</code>
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* formed by adding <code>RowSet</code> objects to a <code>JoinRowSet</code>
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* object.
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* <P>
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* Any standard <code>RowSet</code> implementation <b>may</b> implement
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* the <code>Joinable</code> interface in order to be
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* added to a <code>JoinRowSet</code> object. Implementing this interface gives
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* a <code>RowSet</code> object the ability to use <code>Joinable</code> methods,
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* which set, retrieve, and get information about match columns. An
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* application may add a
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* <code>RowSet</code> object that has not implemented the <code>Joinable</code>
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* interface to a <code>JoinRowSet</code> object, but to do so it must use one
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* of the <code>JoinRowSet.addRowSet</code> methods that takes both a
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* <code>RowSet</code> object and a match column or an array of <code>RowSet</code>
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* objects and an array of match columns.
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* <P>
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* To get access to the methods in the <code>Joinable</code> interface, a
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* <code>RowSet</code> object implements at least one of the
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* five standard <code>RowSet</code> interfaces and also implements the
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* <code>Joinable</code> interface. In addition, most <code>RowSet</code>
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* objects extend the <code>BaseRowSet</code> class. For example:
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* <pre>
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* class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {
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* :
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* :
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* }
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* </pre>
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*
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* <h3>2.0 Usage Guidelines</h3>
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* <P>
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* The methods in the <code>Joinable</code> interface allow a <code>RowSet</code> object
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* to set a match column, retrieve a match column, or unset a match column, which is
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* the column upon which an SQL <code>JOIN</code> can be based.
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* An instance of a class that implements these methods can be added to a
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* <code>JoinRowSet</code> object to allow an SQL <code>JOIN</code> relationship to
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* be established.
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*
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* <pre>
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* CachedRowSet crs = new MyRowSetImpl();
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* crs.populate((ResultSet)rs);
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* (Joinable)crs.setMatchColumnIndex(1);
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*
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* JoinRowSet jrs = new JoinRowSetImpl();
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* jrs.addRowSet(crs);
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* </pre>
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* In the previous example, <i>crs</i> is a <code>CachedRowSet</code> object that
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* has implemented the <code>Joinable</code> interface. In the following example,
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* <i>crs2</i> has not, so it must supply the match column as an argument to the
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* <code>addRowSet</code> method. This example assumes that column 1 is the match
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* column.
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* <PRE>
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* CachedRowSet crs2 = new MyRowSetImpl();
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* crs2.populate((ResultSet)rs);
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*
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* JoinRowSet jrs2 = new JoinRowSetImpl();
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* jrs2.addRowSet(crs2, 1);
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* </PRE>
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* <p>
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* The <code>JoinRowSet</code> interface makes it possible to get data from one or
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* more <code>RowSet</code> objects consolidated into one table without having to incur
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* the expense of creating a connection to a database. It is therefore ideally suited
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* for use by disconnected <code>RowSet</code> objects. Nevertheless, any
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* <code>RowSet</code> object <b>may</b> implement this interface
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* regardless of whether it is connected or disconnected. Note that a
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* <code>JdbcRowSet</code> object, being always connected to its data source, can
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* become part of an SQL <code>JOIN</code> directly without having to become part
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* of a <code>JoinRowSet</code> object.
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*
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* <h3>3.0 Managing Multiple Match Columns</h3>
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* The index array passed into the <code>setMatchColumn</code> methods indicates
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* how many match columns are being set (the length of the array) in addition to
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* which columns will be used for the match. For example:
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* <pre>
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* int[] i = {1, 2, 4, 7}; // indicates four match columns, with column
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* // indexes 1, 2, 4, 7 participating in the JOIN.
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* Joinable.setMatchColumn(i);
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* </pre>
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* Subsequent match columns may be added as follows to a different <code>Joinable</code>
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* object (a <code>RowSet</code> object that has implemented the <code>Joinable</code>
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* interface).
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* <pre>
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* int[] w = {3, 2, 5, 3};
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* Joinable2.setMatchColumn(w);
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* </pre>
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* When an application adds two or more <code>RowSet</code> objects to a
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* <code>JoinRowSet</code> object, the order of the indexes in the array is
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* particularly important. Each index of
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* the array maps directly to the corresponding index of the previously added
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* <code>RowSet</code> object. If overlap or underlap occurs, the match column
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* data is maintained in the event an additional <code>Joinable</code> RowSet is
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* added and needs to relate to the match column data. Therefore, applications
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* can set multiple match columns in any order, but
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* this order has a direct effect on the outcome of the <code>SQL</code> JOIN.
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* <p>
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* This assertion applies in exactly the same manner when column names are used
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* rather than column indexes to indicate match columns.
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*
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* @see JoinRowSet
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* @author Jonathan Bruce
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*/
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public interface Joinable {
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/**
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* Sets the designated column as the match column for this <code>RowSet</code>
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* object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
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* object based on the match column.
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* <p>
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* Sub-interfaces such as the <code>CachedRowSet</code>™
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* interface define the method <code>CachedRowSet.setKeyColumns</code>, which allows
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* primary key semantics to be enforced on specific columns.
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* Implementations of the <code>setMatchColumn(int columnIdx)</code> method
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* should ensure that the constraints on the key columns are maintained when
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* a <code>CachedRowSet</code> object sets a primary key column as a match column.
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*
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* @param columnIdx an <code>int</code> identifying the index of the column to be
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* set as the match column
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* @throws SQLException if an invalid column index is set
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* @see #setMatchColumn(int[])
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* @see #unsetMatchColumn(int)
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*
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*/
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public void setMatchColumn(int columnIdx) throws SQLException;
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/**
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* Sets the designated columns as the match column for this <code>RowSet</code>
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* object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
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* object based on the match column.
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*
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* @param columnIdxes an array of <code>int</code> identifying the indexes of the
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* columns to be set as the match columns
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* @throws SQLException if an invalid column index is set
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* @see #setMatchColumn(int[])
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* @see #unsetMatchColumn(int[])
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*/
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public void setMatchColumn(int[] columnIdxes) throws SQLException;
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/**
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* Sets the designated column as the match column for this <code>RowSet</code>
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* object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
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* object based on the match column.
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* <p>
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* Subinterfaces such as the <code>CachedRowSet</code> interface define
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* the method <code>CachedRowSet.setKeyColumns</code>, which allows
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* primary key semantics to be enforced on specific columns.
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* Implementations of the <code>setMatchColumn(String columnIdx)</code> method
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* should ensure that the constraints on the key columns are maintained when
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* a <code>CachedRowSet</code> object sets a primary key column as a match column.
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*
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* @param columnName a <code>String</code> object giving the name of the column
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* to be set as the match column
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* @throws SQLException if an invalid column name is set, the column name
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* is a null, or the column name is an empty string
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* @see #unsetMatchColumn
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* @see #setMatchColumn(int[])
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*/
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public void setMatchColumn(String columnName) throws SQLException;
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/**
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* Sets the designated columns as the match column for this <code>RowSet</code>
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* object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
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* object based on the match column.
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*
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* @param columnNames an array of <code>String</code> objects giving the names
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* of the column to be set as the match columns
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* @throws SQLException if an invalid column name is set, the column name
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* is a null, or the column name is an empty string
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* @see #unsetMatchColumn
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* @see #setMatchColumn(int[])
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*/
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public void setMatchColumn(String[] columnNames) throws SQLException;
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/**
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* Retrieves the indexes of the match columns that were set for this
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* <code>RowSet</code> object with the method
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* <code>setMatchColumn(int[] columnIdxes)</code>.
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*
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* @return an <code>int</code> array identifying the indexes of the columns
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* that were set as the match columns for this <code>RowSet</code> object
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* @throws SQLException if no match column has been set
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* @see #setMatchColumn
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* @see #unsetMatchColumn
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*/
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public int[] getMatchColumnIndexes() throws SQLException;
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/**
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* Retrieves the names of the match columns that were set for this
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* <code>RowSet</code> object with the method
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* <code>setMatchColumn(String [] columnNames)</code>.
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*
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* @return an array of <code>String</code> objects giving the names of the columns
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* set as the match columns for this <code>RowSet</code> object
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* @throws SQLException if no match column has been set
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* @see #setMatchColumn
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* @see #unsetMatchColumn
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*
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*/
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public String[] getMatchColumnNames() throws SQLException;
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/**
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* Unsets the designated column as the match column for this <code>RowSet</code>
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* object.
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* <P>
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* <code>RowSet</code> objects that implement the <code>Joinable</code> interface
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* must ensure that a key-like constraint continues to be enforced until the
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* method <code>CachedRowSet.unsetKeyColumns</code> has been called on the
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* designated column.
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*
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* @param columnIdx an <code>int</code> that identifies the index of the column
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* that is to be unset as a match column
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* @throws SQLException if an invalid column index is designated or if
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* the designated column was not previously set as a match
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* column
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* @see #setMatchColumn
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*/
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public void unsetMatchColumn(int columnIdx) throws SQLException;
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/**
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* Unsets the designated columns as the match column for this <code>RowSet</code>
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* object.
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*
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* @param columnIdxes an array of <code>int</code> that identifies the indexes
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* of the columns that are to be unset as match columns
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* @throws SQLException if an invalid column index is designated or if
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* the designated column was not previously set as a match
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* column
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* @see #setMatchColumn
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*/
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public void unsetMatchColumn(int[] columnIdxes) throws SQLException;
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/**
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* Unsets the designated column as the match column for this <code>RowSet</code>
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* object.
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* <P>
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* <code>RowSet</code> objects that implement the <code>Joinable</code> interface
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* must ensure that a key-like constraint continues to be enforced until the
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* method <code>CachedRowSet.unsetKeyColumns</code> has been called on the
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* designated column.
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*
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* @param columnName a <code>String</code> object giving the name of the column
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* that is to be unset as a match column
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* @throws SQLException if an invalid column name is designated or
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* the designated column was not previously set as a match
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* column
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* @see #setMatchColumn
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*/
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public void unsetMatchColumn(String columnName) throws SQLException;
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/**
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* Unsets the designated columns as the match columns for this <code>RowSet</code>
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* object.
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*
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* @param columnName an array of <code>String</code> objects giving the names of
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* the columns that are to be unset as the match columns
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* @throws SQLException if an invalid column name is designated or the
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* designated column was not previously set as a match column
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* @see #setMatchColumn
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*/
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public void unsetMatchColumn(String[] columnName) throws SQLException;
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}
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