databasemetadata.java

SSD9 练习9

     * Is "ALTER TABLE" with drop column supported?
     *
     * @return true if so
     */

    public boolean supportsAlterTableWithDropColumn() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Is column aliasing supported?
     *
     * <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.
     *
     * A JDBC compliant driver always returns true.
     *
     * @return true if so
     */

    public boolean supportsColumnAliasing() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Are concatenations between NULL and non-NULL values NULL?
     *
     * A JDBC compliant driver always returns true.
     *
     * @return true if so
     */

    public boolean nullPlusNonNullIsNull() throws java.sql.SQLException 
    {
        return true;  // not sure
    }

    /**
     * Is the CONVERT function between SQL types supported?
     *
     * @return true if so
     */

    public boolean supportsConvert() throws java.sql.SQLException 
    {
        return false; // not sure
    }

    /**
     * Is CONVERT between the given SQL types supported?
     *
     * @param fromType the type to convert from
     * @param toType the type to convert to
     * @return true if so
     * @see Types
     */

    public boolean supportsConvert(int fromType, int toType) 
        throws java.sql.SQLException 
    {
        switch (fromType) {

            /* The char/binary types can be converted
             * to pretty much anything.
             */

        case java.sql.Types.CHAR:
        case java.sql.Types.VARCHAR:
        case java.sql.Types.LONGVARCHAR:
        case java.sql.Types.BINARY:
        case java.sql.Types.VARBINARY:
        case java.sql.Types.LONGVARBINARY:
            switch (toType) {
            case java.sql.Types.DECIMAL:
            case java.sql.Types.NUMERIC:
            case java.sql.Types.REAL:
            case java.sql.Types.TINYINT:
            case java.sql.Types.SMALLINT:
            case java.sql.Types.INTEGER:
            case java.sql.Types.BIGINT: 
            case java.sql.Types.FLOAT:
            case java.sql.Types.DOUBLE:
            case java.sql.Types.CHAR:
            case java.sql.Types.VARCHAR:
            case java.sql.Types.LONGVARCHAR:
            case java.sql.Types.BINARY:
            case java.sql.Types.VARBINARY:
            case java.sql.Types.LONGVARBINARY:
            case java.sql.Types.OTHER:
            case java.sql.Types.DATE:
            case java.sql.Types.TIME:
            case java.sql.Types.TIMESTAMP:
                return true;
            default:
                return false;
            }
          
            /* We don't handle the BIT type
             * yet.
             */

        case java.sql.Types.BIT:
            return false;

            /* The numeric types. Basically they can convert
             * among themselves, and with char/binary types.
             */
         
        case java.sql.Types.DECIMAL:
        case java.sql.Types.NUMERIC:
        case java.sql.Types.REAL:
        case java.sql.Types.TINYINT:
        case java.sql.Types.SMALLINT:
        case java.sql.Types.INTEGER:
        case java.sql.Types.BIGINT:
        case java.sql.Types.FLOAT:
        case java.sql.Types.DOUBLE:
            switch (toType) {
            case java.sql.Types.DECIMAL:
            case java.sql.Types.NUMERIC:
            case java.sql.Types.REAL:
            case java.sql.Types.TINYINT:
            case java.sql.Types.SMALLINT:
            case java.sql.Types.INTEGER:
            case java.sql.Types.BIGINT: 
            case java.sql.Types.FLOAT:
            case java.sql.Types.DOUBLE:
            case java.sql.Types.CHAR:
            case java.sql.Types.VARCHAR:
            case java.sql.Types.LONGVARCHAR:
            case java.sql.Types.BINARY:
            case java.sql.Types.VARBINARY:
            case java.sql.Types.LONGVARBINARY: 
                return true;
            default:
                return false;
            }
          
            /* MySQL doesn't support a NULL type. */
           
        case java.sql.Types.NULL:
            return false;

            /* With this driver, this will always be a serialized
             * object, so the char/binary types will work.
             */

        case java.sql.Types.OTHER:
            switch (toType) {
            case java.sql.Types.CHAR:
            case java.sql.Types.VARCHAR:
            case java.sql.Types.LONGVARCHAR:
            case java.sql.Types.BINARY:
            case java.sql.Types.VARBINARY:
            case java.sql.Types.LONGVARBINARY:
                return true;
            default:
                return false;
            }
         
            /* Dates can be converted to char/binary types. */

        case java.sql.Types.DATE:
            switch (toType) {
            case java.sql.Types.CHAR:
            case java.sql.Types.VARCHAR:
            case java.sql.Types.LONGVARCHAR:
            case java.sql.Types.BINARY:
            case java.sql.Types.VARBINARY:
            case java.sql.Types.LONGVARBINARY:
                return true;
            default:
                return false;
            }
          
            /* Time can be converted to char/binary types */

        case java.sql.Types.TIME:
            switch (toType) {
            case java.sql.Types.CHAR:
            case java.sql.Types.VARCHAR:
            case java.sql.Types.LONGVARCHAR:
            case java.sql.Types.BINARY:
            case java.sql.Types.VARBINARY:
            case java.sql.Types.LONGVARBINARY:
                return true;
            default:
                return false;
            }

            /* Timestamp can be converted to char/binary types
             * and date/time types (with loss of precision).
             */

        case java.sql.Types.TIMESTAMP:
            switch (toType) {
            case java.sql.Types.CHAR:
            case java.sql.Types.VARCHAR:
            case java.sql.Types.LONGVARCHAR:
            case java.sql.Types.BINARY:
            case java.sql.Types.VARBINARY:
            case java.sql.Types.LONGVARBINARY:
            case java.sql.Types.TIME:
            case java.sql.Types.DATE:
                return true;
            default:
                return false;
            }
        
            /* We shouldn't get here! */
          
        default:
            return false; // not sure
        }
    }

    /**
     * Are table correlation names supported?
     *
     * A JDBC compliant driver always returns true.
     *
     * @return true if so
     */

    public boolean supportsTableCorrelationNames() throws java.sql.SQLException 
    {
        return true; // not sure
    }

    /**
     * If table correlation names are supported, are they restricted
     * to be different from the names of the tables?
     *
     * A JDBC compliant driver always returns true.
     *
     * @return true if so
     */

    public boolean supportsDifferentTableCorrelationNames() throws java.sql.SQLException 
    {
        return true; // not sure
    }

    /**
     * Are expressions in "ORDER BY" lists supported?
     *
     * @return true if so
     */

    public boolean supportsExpressionsInOrderBy() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Can an "ORDER BY" clause use columns not in the SELECT?
     *
     * @return true if so
     */

    public boolean supportsOrderByUnrelated() throws java.sql.SQLException 
    {
        return false; // not sure
    }

    /**
     * Is some form of "GROUP BY" clause supported?
     *
     * @return true if so
     */

    public boolean supportsGroupBy() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Can a "GROUP BY" clause use columns not in the SELECT?
     *
     * @return true if so
     */
  
    public boolean supportsGroupByUnrelated() throws java.sql.SQLException 
    {
        return false; // not sure
    }

    /**
     * Can a "GROUP BY" clause add columns not in the SELECT
     * provided it specifies all the columns in the SELECT?
     *
     * @return true if so
     */
        
    public boolean supportsGroupByBeyondSelect() throws java.sql.SQLException 
    {
        return true; // not sure
    }

    /**
     * Is the escape character in "LIKE" clauses supported?
     *
     * A JDBC compliant driver always returns true.
     *
     * @return true if so
     */

    public boolean supportsLikeEscapeClause() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Are multiple ResultSets from a single execute supported?
     *
     * @return true if so
     */

    public boolean supportsMultipleResultSets() throws java.sql.SQLException 
    {
        return false; // not sure
    }
  
    /**
     * Can we have multiple transactions open at once (on different
     * connections)?
     *
     * @return true if so
     */

    public boolean supportsMultipleTransactions() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Can columns be defined as non-nullable?
     *
     * A JDBC compliant driver always returns true.
     *
     * @return true if so
     */

    public boolean supportsNonNullableColumns() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Is the ODBC Minimum SQL grammar supported?
     *
     * All JDBC compliant drivers must return true.
     *
     * @return true if so
     */
        
    public boolean supportsMinimumSQLGrammar() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Is the ODBC Core SQL grammar supported?
     *
     * @return true if so
     */

    public boolean supportsCoreSQLGrammar() throws java.sql.SQLException 
    {
        return true;
    }

    /**
     * Is the ODBC Extended SQL grammar supported?
     *
     * @return true if so
     */
    
    public boolean supportsExtendedSQLGrammar() throws java.sql.SQLException 
    {
        return false; // not sure at all
    }


    /**
     * Is the ANSI92 entry level SQL grammar supported?
     *
     * All JDBC compliant drivers must return true.
     *
     * @return true if so
     */
    
    public boolean supportsANSI92EntryLevelSQL() throws java.sql.SQLException 
    {
        return true;
    }
    
    /**
     * Is the ANSI92 intermediate SQL grammar supported?
     *
     * @return true if so
     */
    
    public boolean supportsANSI92IntermediateSQL() throws java.sql.SQLException 
    {
        return false; // not sure
    }

    /**
     * Is the ANSI92 full SQL grammar supported?
     *
     * @return true if so
     */
    
    public boolean supportsANSI92FullSQL() throws java.sql.SQLException 
    {
        return false; // not sure
    }
    
    /**
     * Is the SQL Integrity Enhancement Facility supported?
     *
     * @return true if so
     */
    
    public boolean supportsIntegrityEnhancementFacility() throws java.sql.SQLException 
    {
        return false; // not sure
    }
    
    /**
     * Is some form of outer join supported?
     *
     * @return true if so
     */
    
    public boolean supportsOuterJoins() throws java.sql.SQLException 
    {
        return true;
    }
    
    /**
     * Are full nested outer joins supported?
     *
     * @return true if so
     */
    
    public boolean supportsFullOuterJoins() throws java.sql.SQLException 
    {
        return false; // not sure
    }
    
    /**
     * Is there limited support for outer joins?  (This will be true
     * if supportFullOuterJoins is true.)
     *
     * @return true if so
     */
    
    public boolean supportsLimitedOuterJoins() throws java.sql.SQLException 
    {
        return true;
    }
    
    /**
     * What's the database vendor's preferred term for "schema"?
     *
     * @return the vendor term
     */
    
    public String getSchemaTerm() throws java.sql.SQLException 
    {
        return "";