statement.java

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/*
 * @(#)Statement.java	1.39 03/01/28
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.sql;

/**
 * <P>The object used for executing a static SQL statement
 * and returning the results it produces.
 * <P>
 * By default, only one <code>ResultSet</code> object per <code>Statement</code>
 * object can be open at the same 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 execution methods in the
 * <code>Statement</code> interface implicitly close a statment's current 
 * <code>ResultSet</code> object if an open one exists.
 *
 * @see Connection#createStatement
 * @see ResultSet 
 */
public interface Statement {

    /**
     * Executes the given SQL statement, which returns a single 
     * <code>ResultSet</code> object.
     *
     * @param sql an SQL statement to be sent to the database, typically 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 or the given
     *            SQL statement produces anything other than a single
     *            <code>ResultSet</code> object
     */
    ResultSet executeQuery(String sql) throws SQLException;

    /**
     * Executes the given SQL statement, which may be an <code>INSERT</code>, 
     * <code>UPDATE</code>, or <code>DELETE</code> statement or an
     * SQL statement that returns nothing, such as an SQL DDL statement.
     *
     * @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 <code>0</code> for SQL statements 
     * that return nothing
     * @exception SQLException if a database access error occurs or the given
     *            SQL statement produces a <code>ResultSet</code> object
     */
    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>
     * Calling the method <code>close</code> on a <code>Statement</code>
     * object that is already closed has no effect.
     * <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;

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

    /**
     * Retrieves the maximum number of bytes that can be
     * returned for character and binary column values in a <code>ResultSet</code> 
     * object produced by this <code>Statement</code> object.
     * This 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 column size limit for columns storing character and 
     *         binary values; zero means there is no limit 
     * @exception SQLException if a database access error occurs
     * @see #setMaxFieldSize
     */
    int getMaxFieldSize() throws SQLException;
    
    /**
     * Sets the limit for the maximum number of bytes in a <code>ResultSet</code>
     * column storing character or binary values to
     * the given number of bytes.  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 column size limit in bytes; zero means there is no limit 
     * @exception SQLException if a database access error occurs 
     *            or the condition max >= 0 is not satisfied
     * @see #getMaxFieldSize
     */
    void setMaxFieldSize(int max) throws SQLException;

    /**
     * Retrieves the maximum number of rows that a
     * <code>ResultSet</code> object produced by this
     * <code>Statement</code> object can contain.  If this limit is exceeded, 
     * the excess rows are silently dropped.
     *
     * @return the current maximum number of rows for a <code>ResultSet</code>
     *         object produced by this <code>Statement</code> object; 
     *         zero means there is no limit
     * @exception SQLException if a database access error occurs
     * @see #setMaxRows
     */
    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 there is no limit 
     * @exception SQLException if a database access error occurs
     *            or the condition max >= 0 is not satisfied
     * @see #getMaxRows
     */
    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 statement to the database.
     *
     * Note: Since prepared statements have usually been parsed prior
     * to making this call, disabling escape processing for 
     * <code>PreparedStatements</code> objects will have no effect.
     *
     * @param enable <code>true</code> to enable escape processing;
     *       <code>false</code> to disable it
     * @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 there is 
     *         no limit 
     * @exception SQLException if a database access error occurs
     * @see #setQueryTimeout
     */
    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 
     *        there is no limit
     * @exception SQLException if a database access error occurs
     *            or the condition seconds >= 0 is not satisfied
     * @see #getQueryTimeout
     */
    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. This method may not be called on a closed
     * <code>Statement</code> object; doing so will cause an <code>SQLException</code>
     * to be thrown.
     *
     * <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 rather than on the <code>Statement</code>
     * object that produced it.
     *
     * @return the first <code>SQLWarning</code> object or <code>null</code> 
     *         if there are no warnings
     * @exception SQLException if a database access error occurs or this 
     *            method is called on a closed statement
     */
    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;

    /**
     * Sets the SQL cursor name to the given <code>String</code>, which 
     * will be used by subsequent <code>Statement</code> object 
     * <code>execute</code> methods. This name can then be
     * used in SQL positioned update or delete statements to identify the
     * current row in the <code>ResultSet</code> object generated by this 
     * statement.  If the database does not 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 have the form <code>SELECT FOR UPDATE</code>.  If 
     * <code>FOR UPDATE</code> is not present, positioned updates may fail.
     *
     * <P><B>Note:</B> By definition, the execution of positioned updates and
     * deletes must be done by a different <code>Statement</code> object than 
     * the one that 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 the given SQL statement, which may return multiple results.
     * In 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.  
     * <P>
     * The <code>execute</code> method executes an SQL statement and indicates the
     * form of the first result.  You must 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 first result is a <code>ResultSet</code> 
     *         object; <code>false</code> if it is an update count or there are 
     *         no results
     * @exception SQLException if a database access error occurs
     * @see #getResultSet
     * @see #getUpdateCount
     * @see #getMoreResults