Quadcap Embeddable Database

com/quadcap/sql/SelectFromItem.java

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package com.quadcap.sql;

/* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import java.util.Vector;

import java.sql.SQLException;

import com.quadcap.util.Debug;

/**
 * TableExpression permitting individual tables in the <code>SELECT</code>
 * statement to be "renamed" via the <code>AS</code> clause.
 * This may be necessary
 * for example, in cases where a table is joined to itself.  The optional
 * column names in the FROM clause can be used to rename columns; this
 * renaming doesn't affect the names of the columns in the final result
 * set, but rather may be used to disambiguate column names in the
 * <code>WHERE</code> clause.</p>
 *
 * @author Stan Bailes
 */
public class SelectFromItem extends TableExpression implements Externalizable {
    TableExpression                     e;
    String                              asName  = null;
    Vector                              columns = null;

    public SelectFromItem() {}

    public SelectFromItem(TableExpression e, String asName, Vector columns) {
        this.e = e;
        this.asName = asName;
        this.columns = columns;
    }

    public void readExternal(ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        this.e = (TableExpression)in.readObject();
        this.asName = (String)in.readObject();
        this.columns = (Vector)in.readObject();
    }
    
    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(e);
        out.writeObject(asName);
        out.writeObject(columns);
    }

    public int rank() { return e.rank(); }

    public boolean isUpdatable() { return e.isUpdatable(); }

    public void getBaseTables(Vector v) {
        e.getBaseTables(v);
    }

    public void setWhere(Expression where) {
        this.where = where;
        e.setWhere(where);
    }

    public Cursor getCursor(Session session, Cursor outer)
        throws SQLException
    {
        Cursor c = e.getCursor(session, outer);
        return new RenameCursor(session, c, asName, columns);
    }

    public String toString() {
        StringBuffer sb = new StringBuffer(e.toString());
        if (asName != null && asName.length() > 0) {
            sb.append(" AS ");
            sb.append(asName);
            if (columns != null) {
                sb.append('(');
                for (int i = 0; i < columns.size(); i++) {
                    if (i > 0) sb.append(',');
                    sb.append(columns.get(i));
                }
                sb.append(')');
            }
        }
        return sb.toString();
    }

    //#ifdef DEBUG
    public String name() {
        StringBuffer sb = new StringBuffer(e.name());
        if (asName != null) {
            sb.append(" AS ");
            sb.append(asName);
        }
        return sb.toString();
    }
    //#endif
}