/*
 * @(#)Statement.java	1.21 00/02/02
 *
 * Copyright 1996-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package java.sql;

/**
 * <P>The object used for executing a static SQL statement
 * and obtaining the results produced by it. 
 *
 * <P>Only one <code>ResultSet</code> object  per <code>Statement</code> object
 * can be open at any point in
 * time. Therefore, if the reading of one <code>ResultSet</code> object is interleaved
 * with the reading of another, each must have been generated by
 * different <code>Statement</code> objects. All statement <code>execute</code> 
 * methods implicitly close a statment's current <code>ResultSet</code> object
 * if an open one exists.
 *
 * @see Connection#createStatement
 * @see ResultSet 
 */
public interface Statement {

    /**
     * Executes an SQL statement that returns a single <code>ResultSet</code> object.
     *
     * @param sql typically this is a static SQL <code>SELECT</code> statement
     * @return a <code>ResultSet</code> object that contains the data produced by the
     * given query; never <code>null</code> 
     * @exception SQLException if a database access error occurs
     */
    ResultSet executeQuery(String sql) throws SQLException;

    /**
     * Executes an SQL <code>INSERT</code>, <code>UPDATE</code> or 
	 * <code>DELETE</code> statement. In addition,
     * SQL statements that return nothing, such as SQL DDL statements,
     * can be executed.
     *
     * @param sql an SQL <code>INSERT</code>, <code>UPDATE</code> or
	 * <code>DELETE</code> statement or an SQL statement that returns nothing
     * @return either the row count for <code>INSERT</code>, <code>UPDATE</code>
	 * or <code>DELETE</code> statements, or 0 for SQL statements that return nothing
     * @exception SQLException if a database access error occurs
     */
    int executeUpdate(String sql) throws SQLException;

    /**
	 * Releases this <code>Statement</code> object's database 
	 * and JDBC resources immediately instead of waiting for
	 * this to happen when it is automatically closed.
     * It is generally good practice to release resources as soon as
	 * you are finished with them to avoid tying up database
	 * resources.
     * <P><B>Note:</B> A <code>Statement</code> object is automatically closed when it is
     * garbage collected. When a <code>Statement</code> object is closed, its current
     * <code>ResultSet</code> object, if one exists, is also closed.  
     *
     * @exception SQLException if a database access error occurs
     */
    void close() throws SQLException;

    //----------------------------------------------------------------------

    /**
     * Returns the maximum number of bytes allowed
     * for any column value. 
	 * This limit is the maximum number of bytes that can be
	 * returned for any column value.
	 * The limit applies only to <code>BINARY</code>,
     * <code>VARBINARY</code>, <code>LONGVARBINARY</code>, <code>CHAR</code>, <code>VARCHAR</code>, and <code>LONGVARCHAR</code>
     * columns.  If the limit is exceeded, the excess data is silently
     * discarded.
     *
     * @return the current max column size limit; zero means unlimited 
     * @exception SQLException if a database access error occurs
     */
    int getMaxFieldSize() throws SQLException;
    
    /**
	 * Sets the limit for the maximum number of bytes in a column to
	 * the given number of bytes.  This is the maximum number of bytes 
	 * that can be returned for any column value.  This limit applies
	 * only to <code>BINARY</code>, <code>VARBINARY</code>,
	 * <code>LONGVARBINARY</code>, <code>CHAR</code>, <code>VARCHAR</code>, and
     * <code>LONGVARCHAR</code> fields.  If the limit is exceeded, the excess data
     * is silently discarded. For maximum portability, use values
     * greater than 256.
     *
     * @param max the new max column size limit; zero means unlimited 
     * @exception SQLException if a database access error occurs
     */
    void setMaxFieldSize(int max) throws SQLException;

    /**
     * Retrieves the maximum number of rows that a
     * <code>ResultSet</code> object can contain.  If the limit is exceeded, the excess
     * rows are silently dropped.
     *
     * @return the current max row limit; zero means unlimited
     * @exception SQLException if a database access error occurs
     */
    int getMaxRows() throws SQLException;

    /**
     * Sets the limit for the maximum number of rows that any
     * <code>ResultSet</code> object can contain to the given number.
	 * If the limit is exceeded, the excess
     * rows are silently dropped.
     *
     * @param max the new max rows limit; zero means unlimited 
     * @exception SQLException if a database access error occurs
     */
    void setMaxRows(int max) throws SQLException;

    /**
	 * Sets escape processing on or off.
     * If escape scanning is on (the default), the driver will do
     * escape substitution before sending the SQL to the database.
     *
     * Note: Since prepared statements have usually been parsed prior
     * to making this call, disabling escape processing for prepared
     * statements will have no effect.
     *
     * @param enable <code>true</code> to enable; <code>false</code> to disable
     * @exception SQLException if a database access error occurs
     */
    void setEscapeProcessing(boolean enable) throws SQLException;

    /**
	 * Retrieves the number of seconds the driver will
     * wait for a <code>Statement</code> object to execute. If the limit is exceeded, a
     * <code>SQLException</code> is thrown.
     *
     * @return the current query timeout limit in seconds; zero means unlimited 
     * @exception SQLException if a database access error occurs
     */
    int getQueryTimeout() throws SQLException;

    /**
     * Sets the number of seconds the driver will
     * wait for a <code>Statement</code> object to execute to the given number of seconds.
	 * If the limit is exceeded, an <code>SQLException</code> is thrown.
     *
     * @param seconds the new query timeout limit in seconds; zero means 
     * unlimited 
     * @exception SQLException if a database access error occurs
     */
    void setQueryTimeout(int seconds) throws SQLException;

    /**
	 * Cancels this <code>Statement</code> object if both the DBMS and
	 * driver support aborting an SQL statement.
     * This method can be used by one thread to cancel a statement that
     * is being executed by another thread.
     *
     * @exception SQLException if a database access error occurs
     */
    void cancel() throws SQLException;

    /**
     * Retrieves the first warning reported by calls on this <code>Statement</code> object.
     * Subsequent <code>Statement</code> object warnings will be chained to this
     * <code>SQLWarning</code> object.
     *
     * <p>The warning chain is automatically cleared each time
     * a statement is (re)executed.
     *
     * <P><B>Note:</B> If you are processing a <code>ResultSet</code> object, any
     * warnings associated with reads on that <code>ResultSet</code> object 
	 * will be chained on it.
     *
     * @return the first <code>SQLWarning</code> object or <code>null</code> 
     * @exception SQLException if a database access error occurs
     */
    SQLWarning getWarnings() throws SQLException;

    /**
	 * Clears all the warnings reported on this <code>Statement</code>
	 * object. After a call to this method,
	 * the method <code>getWarnings</code> will return 
	 * <code>null</code> until a new warning is reported for this
	 * <code>Statement</code> object.  
     *
     * @exception SQLException if a database access error occurs
     */
    void clearWarnings() throws SQLException;

    /**
     * Defines the SQL cursor name that will be used by
     * subsequent <code>Statement</code> object <code>execute</code> methods.
	 * This name can then be
     * used in SQL positioned update/delete statements to identify the
     * current row in the <code>ResultSet</code> object generated by this statement.  If
     * the database doesn't support positioned update/delete, this
     * method is a noop.  To insure that a cursor has the proper isolation
     * level to support updates, the cursor's <code>SELECT</code> statement should be
     * of the form 'select for update ...'. If the 'for update' phrase is 
     * omitted, positioned updates may fail.
     *
     * <P><B>Note:</B> By definition, positioned update/delete
     * execution must be done by a different <code>Statement</code> object than the one
     * which generated the <code>ResultSet</code> object being used for positioning. Also,
     * cursor names must be unique within a connection.
     *
     * @param name the new cursor name, which must be unique within
	 *             a connection
     * @exception SQLException if a database access error occurs
     */
    void setCursorName(String name) throws SQLException;
	
    //----------------------- Multiple Results --------------------------

    /**
     * Executes an SQL statement that may return multiple results.
     * Under some (uncommon) situations a single SQL statement may return
     * multiple result sets and/or update counts.  Normally you can ignore
     * this unless you are (1) executing a stored procedure that you know may
     * return multiple results or (2) you are dynamically executing an
     * unknown SQL string.  The  methods <code>execute</code>,
	 * <code>getMoreResults</code>, <code>getResultSet</code>,
     * and <code>getUpdateCount</code> let you navigate through multiple results.
     *
     * The <code>execute</code> method executes an SQL statement and indicates the
     * form of the first result.  You can then use the methods 
	 * <code>getResultSet</code> or <code>getUpdateCount</code>
	 * to retrieve the result, and <code>getMoreResults</code> to
     * move to any subsequent result(s).
     *
     * @param sql any SQL statement
     * @return <code>true</code> if the next result is a <code>ResultSet</code> object;
	 * <code>false</code> if it is an update count or there are no more results
     * @exception SQLException if a database access error occurs
     * @see #getResultSet
     * @see #getUpdateCount
     * @see #getMoreResults 
     */
    boolean execute(String sql) throws SQLException;
	
    /**
     *  Returns the current result as a <code>ResultSet</code> object. 
     *  This method should be called only once per result.
     *
     * @return the current result as a <code>ResultSet</code> object;
	 * <code>null</code> if the result is an update count or there are no more results
     * @exception SQLException if a database access error occurs
     * @see #execute 
     */
    ResultSet getResultSet() throws SQLException; 

    /**
     *  Returns the current result as an update count;
     *  if the result is a <code>ResultSet</code> object or there are no more results, -1
     *  is returned. This method should be called only once per result.
     * 
     * @return the current result as an update count; -1 if the current result is a
     * <code>ResultSet</code> object or there are no more results
     * @exception SQLException if a database access error occurs
     * @see #execute 
     */
    int getUpdateCount() throws SQLException; 

    /**
     * Moves to a <code>Statement</code> object's next result.  It returns 
	 * <code>true</code> if this result is a <code>ResultSet</code> object.
	 * This method also implicitly closes any current <code>ResultSet</code>
	 * object obtained with the method <code>getResultSet</code>.
     *
     * <P>There are no more results when the following is true:
	 * <PRE>
	 *      <code>(!getMoreResults() && (getUpdateCount() == -1)</code>
	 * </PRE>
     *
     * @return <code>true</code> if the next result is a <code>ResultSet</code> object;
	 * <code>false</code> if it is an update count or there are no more results
     * @exception SQLException if a database access error occurs
     * @see #execute 
     */
    boolean getMoreResults() throws SQLException; 


    //--------------------------JDBC 2.0-----------------------------


    /**
     * Gives the driver a hint as to the direction in which
	 * the rows in a result set
     * will be processed. The hint applies only to result sets created 
     * using this <code>Statement</code> object.  The default value is 
     * <code>ResultSet.FETCH_FORWARD</code>.
     * <p>Note that this method sets the default fetch direction for 
	 * result sets generated by this <code>Statement</code> object.
	 * Each result set has its own methods for getting and setting
	 * its own fetch direction.
     * @param direction the initial direction for processing rows
     * @exception SQLException if a database access error occurs
	 * or the given direction
     * is not one of <code>ResultSet.FETCH_FORWARD</code>,
	 * <code>ResultSet.FETCH_REVERSE</code>, or <code>ResultSet.FETCH_UNKNOWN</code>
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    void setFetchDirection(int direction) throws SQLException;

    /**
     * Retrieves the direction for fetching rows from
	 * database tables that is the default for result sets
	 * generated from this <code>Statement</code> object.
	 * If this <code>Statement</code> object has not set
	 * a fetch direction by calling the method <code>setFetchDirection</code>,
	 * the return value is implementation-specific.
     *
     * @return the default fetch direction for result sets generated
	 *          from this <code>Statement</code> object
     * @exception SQLException if a database access error occurs
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    int getFetchDirection() throws SQLException;

    /**
     * Gives the JDBC driver a hint as to the number of rows that should 
     * be fetched from the database when more rows are needed.  The number 
     * of rows specified affects only result sets created using this 
     * statement. If the value specified is zero, then the hint is ignored.
     * The default value is zero.
     *
     * @param rows the number of rows to fetch
     * @exception SQLException if a database access error occurs, or the
     * condition 0 <= rows <= this.getMaxRows() is not satisfied.
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    void setFetchSize(int rows) throws SQLException;
  
    /**
     * Retrieves the number of result set rows that is the default 
	 * fetch size for result sets
	 * generated from this <code>Statement</code> object.
	 * If this <code>Statement</code> object has not set
	 * a fetch size by calling the method <code>setFetchSize</code>,
	 * the return value is implementation-specific.
     * @return the default fetch size for result sets generated
	 *          from this <code>Statement</code> object
     * @exception SQLException if a database access error occurs
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    int getFetchSize() throws SQLException;

    /**
     * Retrieves the result set concurrency for <code>ResultSet</code> objects
	 * generated by this <code>Statement</code> object.
	 *
	 * @return either <code>ResultSet.CONCUR_READ_ONLY</code> or
	 * <code>ResultSet.CONCUR_UPDATABLE</code>
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    int getResultSetConcurrency() throws SQLException;

    /**
     * Retrieves the result set type for <code>ResultSet</code> objects
	 * generated by this <code>Statement</code> object.
	 *
	 * @return one of <code>ResultSet.TYPE_FORWARD_ONLY</code>,
	 * <code>ResultSet.TYPE_SCROLL_INSENSITIVE</code>, or	
	 * <code>ResultSet.TYPE_SCROLL_SENSITIVE</code>
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    int getResultSetType()  throws SQLException;

    /**
     * Adds an SQL command to the current batch of commmands for this
	 * <code>Statement</code> object. This method is optional.
     *
     * @param sql typically this is a static SQL <code>INSERT</code> or 
	 * <code>UPDATE</code> statement
     * @exception SQLException if a database access error occurs, or the
     * driver does not support batch statements
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    void addBatch( String sql ) throws SQLException;

    /**
     * Makes the set of commands in the current batch empty.
     * This method is optional.
     *
     * @exception SQLException if a database access error occurs or the
     * driver does not support batch statements
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    void clearBatch() throws SQLException;

    /**
     * Submits a batch of commands to the database for execution and
	 * if all commands execute successfully, returns an array of update counts.
	 * The <code>int</code> elements of the array that is returned are ordered
	 * to correspond to the commands in the batch, which are ordered 
	 * according to the order in which they were added to the batch.
	 * The elements in the array returned by the method <code>executeBatch</code>
	 * may be one of the following:
	 * <OL>
	 * <LI>A number greater than or equal to zero -- indicates that the
	 * command was processed successfully and is an update count giving the
	 * number of rows in the database that were affected by the command's
	 * execution
	 * <LI>A value of <code>-2</code> -- indicates that the command was
	 * processed successfully but that the number of rows affected is
	 * unknown
	 * <P> 
	 * If one of the commands in a batch update fails to execute properly,
	 * this method throws a <code>BatchUpdateException</code>, and a JDBC
	 * driver may or may not continue to process the remaining commands in
	 * the batch.  However, the driver's behavior must be consistent with a
	 * particular DBMS, either always continuing to process commands or never
	 * continuing to process commands.  If the driver continues processing
	 * after a failure, the array returned by the method
	 * <code>BatchUpdateException.getUpdateCounts</code>
	 * will contain as many elements as there are commands in the batch, and
	 * at least one of the elements will be the following:
	 * <P> 
	 * <LI>A value of <code>-3</code> -- indicates that the command failed
	 * to execute successfully and occurs only if a driver continues to
	 * process commands after a command fails
	 * </OL>
	 * <P>
     * A driver is not required to implement this method.
	 * The possible implementations and return values have been modified in
	 * the Java 2 SDK, Standard Edition, version 1.3 to
	 * accommodate the option of continuing to proccess commands in a batch
	 * update after a <code>BatchUpdateException</code> obejct has been thrown.
     *
     * @return an array of update counts containing one element for each
     * command in the batch.  The elements of the array are ordered according 
     * to the order in which commands were added to the batch.
     * @exception SQLException if a database access error occurs or the
     * driver does not support batch statements. Throws {@link BatchUpdateException}
	 * (a subclass of <code>SQLException</code>) if one of the commands sent to the
	 * database fails to execute properly or attempts to return a result set.
     * @since 1.3
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    int[] executeBatch() throws SQLException;

    /**
     * Returns the <code>Connection</code> object
	 * that produced this <code>Statement</code> object.
	 * @return the connection that produced this statement
     * @exception SQLException if a database access error occurs
     * @since 1.2
	 * @see <a href="package-summary.html#2.0 API">What Is in the JDBC
	 *      2.0 API</a>
     */
    Connection getConnection()  throws SQLException;
}