jdbcdatabasemetadata.java

hsqldb是100％java实现的数据库,是一个开放源代码的JAVA数据库 l 具有标准的SQL语法和JAVA接口 l HSQLDB可以自由使用和分发 l 非常简洁和快速的

    /**
     * " WHERE 1=1 ". <p>
     *
     * This attribute is in support of methods that use SQL SELECT statements to
     * generate returned <code>ResultSet</code> objects. <p>
     *
     * A good optimizer will simply drop this when parsing a condition
     * expression. And it makes our code much easier to write, since we don't
     * have to check our "WHERE" clause productions as strictly for proper
     * conjunction:  we just stick additional conjunctive predicates on the
     * end of this and Presto! Everything works :-) <p>
     * @since HSQLDB 1.7.2
     */
    private static final String whereTrue = " WHERE 1=1";

    //----------------------------------------------------------------------
    // First, a variety of minor information about the target database.

    /**
     * Retrieves whether the current user can call all the procedures
     * returned by the method <code>getProcedures</code>.  <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * This method still <em>always</em> returns
     * <code>true</code>. <p>
     *
     * In a future release, the plugin interface may be modified to allow
     * implementors to report different values here, based on their
     * implementations.
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean allProceduresAreCallable() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether the current user can use all the tables returned
     * by the method <code>getTables</code> in a <code>SELECT</code>
     * statement.  <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB always reports <code>true</code>.<p>
     *
     * Please note that the default 1.7.2 <code>getTables</code> behaviour is
     * omit from the list of <em>requested</em> tables only those to which the
     * invoking user has <em>no</em> access of any kind. <p>
     *
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean allTablesAreSelectable() throws SQLException {
        return true;
    }

    /**
     * Retrieves the URL for this DBMS.
     *
     *
     * @return the URL for this DBMS or <code>null</code> if it cannot be
     *         generated
     * @exception SQLException if a database access error occurs
     */
    public String getURL() throws SQLException {
        return connection.getURL();
    }

    /**
     * Retrieves the user name as known to this database.
     *
     *
     * @return the database user name
     * @exception SQLException if a database access error occurs
     */
    public String getUserName() throws SQLException {

        ResultSet rs = execute("CALL USER()");

        rs.next();

        String result = rs.getString(1);

        rs.close();

        return result;
    }

    /**
     * Retrieves whether this database is in read-only mode. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Starting with 1.7.2, this makes
     * an SQL call to the new {@link Library#isReadOnlyDatabase} method
     * which provides correct determination of the read-only status for
     * both local and remote database instances.
     * </div>
     * <!-- end release-specific documentation -->
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean isReadOnly() throws SQLException {

        ResultSet rs =
            execute("CALL \"org.hsqldb.Library.isReadOnlyDatabase\"()");

        rs.next();

        boolean result = rs.getBoolean(1);

        rs.close();

        return result;
    }

    /**
     * Retrieves whether <code>NULL</code> values are sorted high.
     * Sorted high means that <code>NULL</code> values
     * sort higher than any other value in a domain.  In an ascending order,
     * if this method returns <code>true</code>,  <code>NULL</code> values
     * will appear at the end. By contrast, the method
     * <code>nullsAreSortedAtEnd</code> indicates whether <code>NULL</code> values
     * are sorted at the end regardless of sort order. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB sorts null low; this method always returns <code>false</code>.
     * </div>
     * <!-- end release-specific documentation -->
     *
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean nullsAreSortedHigh() throws SQLException {
        return false;
    }

    /**
     * Retrieves whether <code>NULL</code> values are sorted low.
     * Sorted low means that <code>NULL</code> values
     * sort lower than any other value in a domain.  In an ascending order,
     * if this method returns <code>true</code>,  <code>NULL</code> values
     * will appear at the beginning. By contrast, the method
     * <code>nullsAreSortedAtStart</code> indicates whether <code>NULL</code> values
     * are sorted at the beginning regardless of sort order. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB sorts null low; this method always returns <code>true</code>.
     * </div>
     * <!-- end release-specific documentation -->
     *
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean nullsAreSortedLow() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether <code>NULL</code> values are sorted at the start regardless
     * of sort order. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB sorts null low; this method always returns <code>false</code>.
     * </div>
     * <!-- end release-specific documentation -->
     *
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean nullsAreSortedAtStart() throws SQLException {
        return false;
    }

    /**
     * Retrieves whether <code>NULL</code> values are sorted at the end regardless of
     * sort order. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB sorts null low; this method always returns <code>false</code>.
     * </div>
     * <!-- end release-specific documentation -->
     *
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean nullsAreSortedAtEnd() throws SQLException {
        return false;
    }

    /**
     * Retrieves the name of this database product. <p>
     *
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Starting with HSQLDB 1.7.2, this value is retrieved through an
     * SQL call to the new {@link Library#getDatabaseProductName} method
     * which allows correct determination of the database product name
     * for both local and remote database instances.
     * </div> <p>
     *
     * @return database product name
     * @exception SQLException if a database access error occurs
     */
    public String getDatabaseProductName() throws SQLException {

        ResultSet rs =
            execute("call \"org.hsqldb.Library.getDatabaseProductName\"()");

        rs.next();

        String result = rs.getString(1);

        rs.close();

        return result;
    }

    /**
     * Retrieves the version number of this database product. <p>
     *
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Starting with HSQLDB 1.7.2, this value is retrieved through an
     * SQL call to the new {@link Library#getDatabaseProductVersion} method
     * which allows correct determination of the database product name
     * for both local and remote database instances.
     * </div> <p>
     *
     * @return database version number
     * @exception SQLException if a database access error occurs
     */
    public String getDatabaseProductVersion() throws SQLException {

        ResultSet rs = execute(
            "call \"org.hsqldb.Library.getDatabaseProductVersion\"()");

        rs.next();

        String result = rs.getString(1);

        rs.close();

        return result;
    }

    /**
     * Retrieves the name of this JDBC driver.
     *
     * @return JDBC driver name
     * @exception SQLException if a database access error occurs
     */
    public String getDriverName() throws SQLException {
        return HsqlDatabaseProperties.PRODUCT_NAME + " Driver";
    }

    /**
     * Retrieves the version number of this JDBC driver as a <code>String</code>.
     *
     * @return JDBC driver version
     * @exception SQLException if a database access error occurs
     */
    public String getDriverVersion() throws SQLException {
        return HsqlDatabaseProperties.THIS_VERSION;
    }

    /**
     * Retrieves this JDBC driver's major version number.
     *
     * @return JDBC driver major version
     */
    public int getDriverMajorVersion() {
        return HsqlDatabaseProperties.MAJOR;
    }

    /**
     * Retrieves this JDBC driver's minor version number.
     *
     * @return JDBC driver minor version number
     */
    public int getDriverMinorVersion() {
        return HsqlDatabaseProperties.MINOR;
    }

    /**
     * Retrieves whether this database stores tables in a local file. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * From HSQLDB 1.7.2 it is assumed that this refers to data being stored
     * by the JDBC client. This method always returns false.
     * </div>
     * <!-- end release-specific documentation -->
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean usesLocalFiles() throws SQLException {
        return false;
    }

    /**