package org.litesoft.orsup.selection;

import org.litesoft.util.IllegalArgument;

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/**
 * A class that can represent a SQL Single Column Select statement.<p>
 *
 * This form of SQL Select statement exists primarily to support the SQL IN
 * <b>WhereClause</b>.<p>
 *
 * See <a href="AbstractWhereClauseColumnIsIn.html">AbstractWhereClauseColumnIsIn</a><br>
 * See <a href="WhereClause.html">WhereClause</a><br>
 * See <a href="WhereClauseFactory.html">WhereClauseFactory</a><p>
 *
 * Exceptions: All problems caught when the parameter(s) are checked (as
 * indicated/implied in the @param tags) will generate an IllegalArgumentException,
 * and means the API user has a problem.  If a NullPointerException (or some
 * others, like: ClassCastException or ArrayIndexOutOfBoundsException) is thrown,
 * it means the API developer has a problem.  Any Exception that is explicitly
 * thrown in the API, but unrelated to a parameter, will be listed in the throws
 * clause (and hopefully in the tag @throws).  These may (but probably won't) be
 * checked Exceptions.
 *
 * @author  George Smith
 * @version 1.03 02/07/02 Exception Policy, Use of IllegalArgument class.
 * @version 1.02 11/05/01 Completed? JavaDocs
 * @version 1.01 10/10/01
 * @version 1.0 10/07/01
 */

public class SingleColumnSelect
{
    private SimpleColumnDefinition zColumnDefinition;
    private String zTableName;
    private WhereClause zWhereClause;

    /**
     * Constructor that supports the generation of a SQL Select statment that
     * selects a single column for all rows.<p>
     *
     * @param   pColumnDefinition   Column Definition (!null).
     * @param   pFromTable          Table Identifier (supports getTableName()) (!null).
     */
    public SingleColumnSelect( SimpleColumnDefinition pColumnDefinition , SimpleTableIdentifier pFromTable )
    {
        this( pColumnDefinition , pFromTable , null );
    }

    /**
     * Constructor that supports the generation of a SQL Select statment that
     * selects a single column for the specified rows.<p>
     *
     * @param   pColumnDefinition   Column Definition (!null).
     * @param   pFromTable          Table Identifier (supports getTableName()) (!null).
     * @param   pWhereClause        A Where Clause to select the appropriate rows (null ok).
     */
    public SingleColumnSelect( SimpleColumnDefinition pColumnDefinition , SimpleTableIdentifier pFromTable , WhereClause pWhereClause )
    {
        IllegalArgument.ifNull( "ColumnDefinition" , zColumnDefinition = pColumnDefinition);
        IllegalArgument.ifNull( "TableIdentifier" , pFromTable );
        IllegalArgument.ifNull( "TableName" , zTableName = pFromTable.getTableName());
        zWhereClause = pWhereClause; // Null OK!
    }

    /**
     * Accessor for the Column Definition of <b>the</b> selected column.<p>
     *
     * @return The selected Column Definition (!null).
     */
    public final SimpleColumnDefinition getColumnDefinition()
    {
        return zColumnDefinition;
    }

    /**
     * Accessor for the Table Name.<p>
     *
     * @return The Table Name (!null).
     */
    public final String getTableName()
    {
        return zTableName;
    }

    /**
     * Accessor for the WhereClause to limit the select the rows.<p>
     *
     * @return Select's WhereClause (null == all rows).
     */
    public final WhereClause getWhereClause()
    {
        return zWhereClause;
    }

    /**
     * Generate a Debug friendly representation.<p>
     *
     * @return a String for Debuging.
     */
    public final String toString()
    {
        StringBuffer sb = new StringBuffer( "Select " );
        sb.append( zColumnDefinition.getName() );
        sb.append( " From " );
        sb.append( zTableName );
        if ( zWhereClause != null )
        {
            sb.append( ' ' );
            sb.append( zWhereClause.toString() );
        }
        return sb.toString();
    }

    /**
     * Generate a String that may be used as a SQL statement that selects a
     * single column.<p>
     *
     * Note: This String can get quite large.<p>
     *
     * @return a single column SQL SELECT statement.
     */
    public final String toSQL()
    {
        StringBuffer sb = new StringBuffer( "SELECT " );
        sb.append( zColumnDefinition.getColumnName() );
        sb.append( " FROM " );
        sb.append( zTableName );
        if ( zWhereClause != null )
        {
            sb.append( ' ' );
            sb.append( zWhereClause.toSQL() );
        }
        return sb.toString();
    }
}