Oracle

Low level Oracle server interface

The low level Oracle server interface exists of one unit, oraoci, which is a straight translation of the Oracle interface header files.

There are 2 example programs:

• oraclew contains some utility routines for the oracle interface, for easier management of result sets. Needs the classes unit from the FCL.
• test01 a simple test program to demonstrate the interface.

OOP access to Oracle

Built over the low-level interface, the SQLDB framework supplied with FPC supports accessing Oracle (using TOracleConnection); see also Lazarus_Database_Overview#Lazarus_and_Oracle

Lazarus also has a component:

• Hostname: as with other sqldb connectors, use hostname or IP address. Leave empty if you use a TNSNNAMES.ORA net service name in DatabaseName
• Username/password: same as with other sqldb connectors
• DatabaseName:
  • instance/SID of the Oracle server you want to connect to or
  • net service name in a TNSNAMES.ORA file

  Note: Released FPC/Lazarus x64 versions on Windows do not include an Oracle connector. If you enable it and test successfully, please submit a patch with the changes so it can be included

Troubleshooting

Client and server character sets

To get info about what character set/NLS settings are active, you can run the following program.

Please don't forget to fill out correct server name, username, password and database name before compiling.

program oracharset;

{ Shows client and server character set/NLS info}
{ PLEASE EDIT PASSWORDS ETC BELOW. }

{$mode objfpc}{$H+}

uses {$IFDEF UNIX} {$IFDEF UseCThreads}
  cthreads, {$ENDIF} {$ENDIF}
  Classes,
  SysUtils,
  sqldb,
  oracleconnection;

var
  Col: integer;
  Conn: TOracleConnection;
  Tran: TSQLTransaction;
  Q: TSQLQuery;
begin
  Conn := TOracleConnection.Create(nil);
  Tran := TSQLTransaction.Create(nil);
  Q := TSQLQuery.Create(nil);
  try
    // * EDIT IDENTIFYING INFO AS NEEDED*
    Conn.HostName := '';
    Conn.UserName := 'system';
    Conn.Password := '';
    Conn.DatabaseName := 'XE';
    // *END IDENTIFIYING INFO*
    Conn.Transaction := Tran;
    Q.DataBase := Conn;
    Conn.Open;
    Tran.Active := true;

    writeln('Server character set info:');
    Q.SQL.Text := 'SELECT value$ FROM sys.props$ WHERE name like ''NLS_%'' ';
    Q.Open;
    Q.First;
    while not (Q.EOF) do
    begin
      writeln('*****************');
      for Col := 0 to Q.Fields.Count - 1 do
      begin
        try
          writeln(Q.Fields[Col].DisplayLabel + ':');
          writeln(Q.Fields[Col].AsString);
        except
          writeln('Error retrieving field ', Col);
        end;
      end;
      Q.Next;
    end;
    Q.Close;

    writeln('');
    writeln('Client character set info:');
    Q.SQL.Text := 'SELECT * FROM NLS_SESSION_PARAMETERS ';
    Q.Open;
    Q.First;
    while not (Q.EOF) do
    begin
      writeln('*****************');
      for Col := 0 to Q.Fields.Count - 1 do
      begin
        try
          writeln(Q.Fields[Col].DisplayLabel + ':');
          writeln(Q.Fields[Col].AsString);
        except
          writeln('Error retrieving field ', Col);
        end;
      end;
      Q.Next;
    end;
    Q.Close;
    // *END EXAMPLE BUG TESTING CODE*
    Conn.Close;
  finally
    Q.Free;
    Tran.Free;
    Conn.Free;
  end;
  writeln('Program complete. Press a key to continue.');
  readln;
end.

ORA-00911 : invalid character

If you see this error message, you might want to try

• removing a trailing semicolon - ; - if you have it in a SELECT statement
• adding a trailing semicolon (e.g. in CALL or EXECUTE statements)

See this thread which applies to .Net but may apply to SQLDB as well: [1]

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