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

     * with add column. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * From 1.7.0, HSQLDB supports this type of
     * <code>ALTER TABLE</code> statement; 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 supportsAlterTableWithAddColumn() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports <code>ALTER TABLE</code>
     * with drop column. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * From 1.7.0, HSQLDB supports this type of
     * <code>ALTER TABLE</code> statement; 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 supportsAlterTableWithDropColumn() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports column aliasing.
     *
     * <P>If so, the SQL AS clause can be used to provide names for
     * computed columns or to provide alias names for columns as
     * required. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports column aliasing; 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 supportsColumnAliasing() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports concatenations between
     * <code>NULL</code> and non-<code>NULL</code> values being
     * <code>NULL</code>. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports this; 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 nullPlusNonNullIsNull() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports the <code>CONVERT</code>
     * function between SQL types. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports conversions; 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 supportsConvert() throws SQLException {
        return true;
    }

// fredt@users - JD comment - I think this is unsupported at the moment
// because SQL92 says conversion is implementation dependent, so if
// conversion from DOUBLE to INTEGER were possbible we would return the
// whole number part, but we currently throw. I'm not so sure about
// conversions between string and numeric where it is logically possible
// only if the string represents a numeric value

    /**
     * Retrieves whether this database supports the <code>CONVERT</code>
     * for two given SQL types. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports conversion though String intermediates, so everything
     * should be possible, short of number format errors (all Java objects
     * have a toString method); this method always returns <code>true</code>.
     * </div>
     * <!-- end release-specific documentation -->
     *
     *
     * @param fromType the type to convert from; one of the type codes from
     *       the class <code>java.sql.Types</code>
     * @param toType the type to convert to; one of the type codes from
     *       the class <code>java.sql.Types</code>
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     * @see java.sql.Types
     */
    public boolean supportsConvert(int fromType,
                                   int toType) throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports table correlation names. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports table correlation names; 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 supportsTableCorrelationNames() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether, when table correlation names are supported, they
     * are restricted to being different from the names of the tables. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB requires that table correlation names are different from the
     * names of the tables; 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 supportsDifferentTableCorrelationNames()
    throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports expressions in
     * <code>ORDER BY</code> lists. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports expressions in <code>ORDER BY</code> lists; 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 supportsExpressionsInOrderBy() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports using a column that is
     * not in the <code>SELECT</code> statement in an
     * <code>ORDER BY</code> clause. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports using a column that is not in the <code>SELECT</code>
     * statement in an <code>ORDER BY</code> clause; 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 supportsOrderByUnrelated() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports some form of
     * <code>GROUP BY</code> clause. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports using the <code>GROUP BY</code> clause; 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 supportsGroupBy() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports using a column that is
     * not in the <code>SELECT</code> statement in a
     * <code>GROUP BY</code> clause. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports using a column that is
     * not in the <code>SELECT</code> statement in a
     * <code>GROUP BY</code> clause; 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 supportsGroupByUnrelated() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports using columns not included in
     * the <code>SELECT</code> statement in a <code>GROUP BY</code> clause
     * provided that all of the columns in the <code>SELECT</code> statement
     * are included in the <code>GROUP BY</code> clause. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports using columns not included in
     * the <code>SELECT</code> statement in a <code>GROUP BY</code> clause
     * provided that all of the columns in the <code>SELECT</code> statement
     * are included in the <code>GROUP BY</code> clause; 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 supportsGroupByBeyondSelect() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports specifying a
     * <code>LIKE</code> escape clause. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * HSQLDB supports specifying a
     * <code>LIKE</code> escape clause; 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 supportsLikeEscapeClause() throws SQLException {
        return true;
    }

    /**
     * Retrieves whether this database supports getting multiple
     * <code>ResultSet</code> objects from a single call to the
     * method <code>execute</code>. <p>
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Up to and including 1.7.2, HSQLDB does not support getting multiple
     * <code>ResultSet</code> objects from a single call to the
     * method <code>execute</code>; this method
     * always returns <code>false</code>. <p>
     *
     * This behaviour <i>may</i> change in a future release.
     * </div>