Medium-level Interface

The Silk Performer medium-level interface provides access to DBMSs via ODBC. The medium-level interface gives you more control when accessing the database than is possible with the high-level interface.

The main characteristics of the medium-level interface are:

• DB_Api functions work with SQL commands defined in the dclsql section. See Datatype SQL.

• Automatic binding is supported.

• Automatic error handling is provided.

• Cursors must be declared explicitly (in contrast to the high-level interface). See Datatype cursor.

• Multiple connects to DBMSs are possible within a single transaction.

Example

The following example shows the TSelling transaction from above using the medium-level interface.

use "DBAPI.bdh";

dclrand
  rAno: RndUniN(1..2000);

var
  hDBC1, ano, stock : number;
  c1, c2 : cursor;

dcltrans
  transaction DBApiSelling
  var
    i      : number;
    bFirst : boolean init true;
  begin
    if bFirst then //connecting, only executed on first call
      bFirst := false;
      hDBC1 := DB_Connect("dsn=sample;uid=u1;pwd=u1");
      SQLSetConnectOption(hDBC1, SQL_AUTOCOMMIT, 0);
      DB_AllocCursor(hDBC1, c1);
      DB_AllocCursor(hDBC1, c2);
      DB_Prepare(c1, SelArticle);
      DB_Prepare(c2, UpdStock);
    end;

    for i := 1 to RndUniN(4..7) do
      ano := rAno;
      DB_Execute(c1);
      fetch c1 next 1;
      DB_Execute(c2);
    end;

    DB_Commit(hDBC1);
  end DBApiSelling;

dclsql
  SelArticle:
  SELECT a_name, a_cat, a_price, a_stock
  INTO *, *, *, :stock FROM article
  WHERE a_no = :ano;
  UpdStock:
  UPDATE article SET a_stock = 99999
  WHERE a_no = :ano;

The medium-level interface consists of the following database access functions (DB_Api functions):