The Implicit Connection with DATABASE Statements

If one of these database statements is the first SQL statement in an application, the statement establishes a connection to a database server, which is known as an implicit connection. If the database statement specifies only a database name, the database server name is obtained from the DBPATH environment variable. This situation is described in Specifying the Database Environment.

An application that makes an implicit connection can establish other connections explicitly (using the CONNECT statement) but cannot establish another implicit connection unless the original implicit connection is closed. An application can terminate an implicit connection using the DISCONNECT statement. After you create an explicit connection, you cannot use any database statement to create implicit connections until after you close the explicit connection.

After any implicit connection is made, that connection is considered to be the default connection, regardless of whether the database server is the default that the INFORMIXSERVER environment variable specifies. This feature allows the application to refer to the implicit connection if additional explicit connections are made, because the implicit connection has no identifier.

For example, if you establish an implicit connection followed by an explicit connection, you can make the implicit connection current by issuing the SET CONNECTION DEFAULT statement. This means, however, that once you establish an implicit connection, you cannot use the CONNECT DEFAULT statement, because the implicit connection is now the default connection.

The database statements can always be used to open a database or create a new database on the current database server.