jdbcdatabasemetadata.java

一个用java写的开源的数据库系统

     *
     *
     * @return <code>true</code> if so; <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    public boolean storesMixedCaseQuotedIdentifiers() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return false;

        // No: as case sensitive.
    }

    /**
     * Retrieves the string used to quote SQL identifiers.
     * This method returns a space " " if identifier quoting is not supported. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * HSQLDB uses the standard SQL identifer quote character
     * (the double qoute character); this method always returns <b>"</b>.
     * </span>
     * <!-- end release-specific documentation -->
     *
     *
     * @return the quoting string or a space if quoting is not supported
     * @exception SQLException if a database access error occurs
     */
    public String getIdentifierQuoteString() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return "\"";

        // InterBase (iscdrv32.dll) returns ""
    }

//fredt@users 20020429 - JavaDoc comment - in 1.7.1 there are keywords such
// as TEMP, TEXT, CACHED that are not SQL 92 keywords

    /**
     * Retrieves a comma-separated list of all of this database's SQL keywords
     * that are NOT also SQL92 keywords. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * The list returned contains HSQLDB keywords that are not in the list
     * of reserved words. Some of these are in the list of potential reserved
     * words that are not SQL92 keywords, but are reported in the
     * standard as possible future SQL keywords.
     * </span>
     * <!-- end release-specific documentation -->
     *
     *
     * @return the list of this database's keywords that are not also
     *       SQL92 keywords
     * @exception SQLException if a database access error occurs
     */
    public String getSQLKeywords() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return "BEFORE,BIGINT,BINARY,CACHED,DATETIME,"
               + "LIMIT,LONGVARBINARY,LONGVARCHAR,OBJECT,OTHER,SAVEPOINT,"
               + "TEMP,TEXT,TRIGGER,TINYINT,VARBINARY,VARCHAR_IGNORECASE";
    }

    /**
     * Retrieves a comma-separated list of math functions available with
     * this database.  These are the Open /Open CLI math function names used in
     * the JDBC function escape clause.
     * @return the list of math functions supported by this database
     * @exception SQLException if a database access error occurs
     */
    public String getNumericFunctions() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return StringUtil.getList(Library.sNumeric, ",", "");
    }

    /**
     * Retrieves a comma-separated list of string functions available with
     * this database.  These are the  Open Group CLI string function names used
     * in the JDBC function escape clause.
     * @return the list of string functions supported by this database
     * @exception SQLException if a database access error occurs
     */
    public String getStringFunctions() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return StringUtil.getList(Library.sString, ",", "");
    }

    /**
     * Retrieves a comma-separated list of system functions available with
     * this database.  These are the  Open Group CLI system function names used
     * in the JDBC function escape clause.
     * @return a list of system functions supported by this database
     * @exception SQLException if a database access error occurs
     */
    public String getSystemFunctions() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return StringUtil.getList(Library.sSystem, ",", "");
    }

    /**
     * Retrieves a comma-separated list of the time and date functions available
     * with this database.
     * @return the list of time and date functions supported by this database
     * @exception SQLException if a database access error occurs
     */
    public String getTimeDateFunctions() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return StringUtil.getList(Library.sTimeDate, ",", "");
    }

    /**
     * Retrieves the string that can be used to escape wildcard characters.
     * This is the string that can be used to escape '_' or '%' in
     * the catalog search parameters that are a pattern (and therefore use one
     * of the wildcard characters).
     *
     * <P>The '_' character represents any single character;
     * the '%' character represents any sequence of zero or
     * more characters. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * Up to and including 1.7.1, HSQLDB uses the "\" character to escape
     * wildcard characters.
     * </span>
     * <!-- end release-specific documentation -->
     *
     *
     * @return the string used to escape wildcard characters
     * @exception SQLException if a database access error occurs
     */
    public String getSearchStringEscape() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return "\\";
    }

    /**
     * Retrieves all the "extra" characters that can be used in unquoted
     * identifier names (those beyond a-z, A-Z, 0-9 and _). <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * Up to and including 1.7.1, HSQLDB does not support using any
     * "extra" characters in unquoted identifier names; this method always
     * returns the empty String.
     * </span>
     * <!-- end release-specific documentation -->
     *
     *
     * @return the string containing the extra characters
     * @exception SQLException if a database access error occurs
     */
    public String getExtraNameCharacters() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return "";
    }

    //--------------------------------------------------------------------
    // Functions describing which features are supported.

    /**
     * Retrieves whether this database supports <code>ALTER TABLE</code>
     * with add column. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * From 1.7.0, HSQLDB support this type of
     * <code>ALTER TABLE</code> statement; this method always
     * returns <code>true</code>.
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return true;
    }

    /**
     * Retrieves whether this database supports <code>ALTER TABLE</code>
     * with drop column. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * From 1.7.0, HSQLDB support this type of
     * <code>ALTER TABLE</code> statement; this method always
     * returns <code>true</code>.
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        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 -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * HSQLDB supports column aliasing; this method always
     * returns <code>true</code>.
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return true;

        // InterBase (iscdrv32.dll) returns false
    }

    /**
     * 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 -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * HSQLDB supports this; this method always
     * returns <code>true</code>.
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return true;

        // Access (odbcjt32.dll) returns false
    }

    /**
     * Retrieves whether this database supports the <code>CONVERT</code>
     * function between SQL types. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * HSQLDB supports conversions; this method always
     * returns <code>true</code>.
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        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 -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <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>.
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        return true;
    }

    /**
     * Retrieves whether this database supports table correlation names. <p>
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>