databasemetadata.java

关系型数据库 Postgresql 6.5.2

  /**
   * This is the string that can be used to escape '_' and '%' in
   * a search string pattern style catalog search parameters
   *
   * @return the string used to escape wildcard characters
   * @exception SQLException if a database access error occurs
   */
  public String getSearchStringEscape() throws SQLException
  {
    return new String("\\");
  }
  
  /**
   * Get all the "extra" characters that can bew used in unquoted
   * identifier names (those beyond a-zA-Z0-9 and _)
   *
   * <p>From the file src/backend/parser/scan.l, an identifier is
   * {letter}{letter_or_digit} which makes it just those listed
   * above.
   *
   * @return a string containing the extra characters
   * @exception SQLException if a database access error occurs
   */
  public String getExtraNameCharacters() throws SQLException
  {
    return new String("");
  }
  
  /**
   * Is "ALTER TABLE" with an add column supported?
   * Yes for PostgreSQL 6.1
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsAlterTableWithAddColumn() throws SQLException
  {
    return true;
  }
  
  /**
   * Is "ALTER TABLE" with a drop column supported?
   * Yes for PostgreSQL 6.1
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsAlterTableWithDropColumn() throws 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.
   *
   * <p>e.g.
   *
   * <br><pre>
   * select count(C) as C_COUNT from T group by C;
   *
   * </pre><br>
   * should return a column named as C_COUNT instead of count(C)
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsColumnAliasing() throws SQLException
  {
    return true;
  }
  
  /**
   * Are concatenations between NULL and non-NULL values NULL?  A
   * JDBC Compliant driver always returns true
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean nullPlusNonNullIsNull() throws SQLException
  {
    return true;
  }
  
  public boolean supportsConvert() throws SQLException
  {
    // XXX-Not Implemented
    return false;
  }
  
  public boolean supportsConvert(int fromType, int toType) throws SQLException
  {
    // XXX-Not Implemented
    return false;
  }
  
  public boolean supportsTableCorrelationNames() throws SQLException
  {
    // XXX-Not Implemented
    return false;
  }
  
  public boolean supportsDifferentTableCorrelationNames() throws SQLException
  {
    // XXX-Not Implemented
    return false;
  }
  
  /**
   * Are expressions in "ORCER BY" lists supported?
   * 
   * <br>e.g. select * from t order by a + b;
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsExpressionsInOrderBy() throws SQLException
  {
    return true;
  }
  
  /**
   * Can an "ORDER BY" clause use columns not in the SELECT?
   * I checked it, and you can't.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsOrderByUnrelated() throws SQLException
  {
    return false;
  }
  
  /**
   * Is some form of "GROUP BY" clause supported?
   * I checked it, and yes it is.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsGroupBy() throws SQLException
  {
    return true;
  }
  
  /**
   * Can a "GROUP BY" clause use columns not in the SELECT?
   * I checked it - it seems to allow it
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsGroupByUnrelated() throws SQLException
  {
    return true;
  }
  
  /**
   * Can a "GROUP BY" clause add columns not in the SELECT provided
   * it specifies all the columns in the SELECT?  Does anyone actually
   * understand what they mean here?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsGroupByBeyondSelect() throws SQLException
  {
    return true;		// For now...
  }
  
  /**
   * Is the escape character in "LIKE" clauses supported?  A
   * JDBC compliant driver always returns true.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsLikeEscapeClause() throws SQLException
  {
    return true;
  }
  
  /**
   * Are multiple ResultSets from a single execute supported?
   * Well, I implemented it, but I dont think this is possible from
   * the back ends point of view.
   * 
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsMultipleResultSets() throws SQLException
  {
    return false;
  }
  
  /**
   * Can we have multiple transactions open at once (on different
   * connections?)
   * I guess we can have, since Im relying on it.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsMultipleTransactions() throws SQLException
  {
    return true;
  }
  
  /**
   * Can columns be defined as non-nullable.  A JDBC Compliant driver
   * always returns true.
   *
   * <p>This changed from false to true in v6.2 of the driver, as this
   * support was added to the backend.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsNonNullableColumns() throws SQLException
  {
    return true;
  }
  
  /**
   * Does this driver support the minimum ODBC SQL grammar.  This
   * grammar is defined at:
   *
   * <p><a href="http://www.microsoft.com/msdn/sdk/platforms/doc/odbc/src/intropr.htm">http://www.microsoft.com/msdn/sdk/platforms/doc/odbc/src/intropr.htm</a>
   *
   * <p>In Appendix C.  From this description, we seem to support the
   * ODBC minimal (Level 0) grammar.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsMinimumSQLGrammar() throws SQLException
  {
    return true;
  }
  
  /**
   * Does this driver support the Core ODBC SQL grammar.  We need
   * SQL-92 conformance for this.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsCoreSQLGrammar() throws SQLException
  {
    return false;
  }
  
  /**
   * Does this driver support the Extended (Level 2) ODBC SQL
   * grammar.  We don't conform to the Core (Level 1), so we can't
   * conform to the Extended SQL Grammar.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsExtendedSQLGrammar() throws SQLException
  {
    return false;
  }
  
  /**
   * Does this driver support the ANSI-92 entry level SQL grammar?
   * All JDBC Compliant drivers must return true.  I think we have
   * to support outer joins for this to be true.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsANSI92EntryLevelSQL() throws SQLException
  {
    return false;
  }
  
  /**
   * Does this driver support the ANSI-92 intermediate level SQL
   * grammar?  Anyone who does not support Entry level cannot support
   * Intermediate level.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsANSI92IntermediateSQL() throws SQLException
  {
    return false;
  }
  
  /**
   * Does this driver support the ANSI-92 full SQL grammar?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsANSI92FullSQL() throws SQLException
  {
    return false;
  }
  
  /**
   * Is the SQL Integrity Enhancement Facility supported?
   * I haven't seen this mentioned anywhere, so I guess not
   * 
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsIntegrityEnhancementFacility() throws SQLException
  {
    return false;
  }
  
  /**
   * Is some form of outer join supported?  From my knowledge, nope.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsOuterJoins() throws SQLException
  {
    return false;
  }
  
  /**
   * Are full nexted outer joins supported?  Well, we dont support any
   * form of outer join, so this is no as well
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsFullOuterJoins() throws SQLException
  {
    return false;
  }
  
  /**
   * Is there limited support for outer joins?  (This will be true if
   * supportFullOuterJoins is true)
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsLimitedOuterJoins() throws SQLException
  {
    return false;
  }
  
  /**
   * What is the database vendor's preferred term for "schema" - well,
   * we do not provide support for schemas, so lets just use that
   * term.
   *
   * @return the vendor term
   * @exception SQLException if a database access error occurs
   */
  public String getSchemaTerm() throws SQLException
  {
    return new String("Schema");
  }
  
  /**
   * What is the database vendor's preferred term for "procedure" - 
   * I kind of like "Procedure" myself.
   *
   * @return the vendor term
   * @exception SQLException if a database access error occurs
   */
  public String getProcedureTerm() throws SQLException
  {
    return new String("Procedure");
  }
  
  /**
   * What is the database vendor's preferred term for "catalog"? -
   * we dont have a preferred term, so just use Catalog
   *
   * @return the vendor term
   * @exception SQLException if a database access error occurs
   */
  public String getCatalogTerm() throws SQLException
  {
    return new String("Catalog");
  }
  
  /**
   * Does a catalog appear at the start of a qualified table name?
   * (Otherwise it appears at the end).
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean isCatalogAtStart() throws SQLException
  {
    return false;
  }
  
  /**
   * What is the Catalog separator.  Hmmm....well, I kind of like
   * a period (so we get catalog.table definitions). - I don't think
   * PostgreSQL supports catalogs anyhow, so it makes no difference.
   *
   * @return the catalog separator string
   * @exception SQLException if a database access error occurs
   */
  public String getCatalogSeparator() throws SQLException
  {
    // PM Sep 29 97 - changed from "." as we don't support catalogs.
    return new String("");