HOpenConnection (Function)

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Syntax 1: Opening a preset connection: automatic management of connections
Syntax 2: Using a character string for the OLE DB provider
Syntax 2 and 3: If a failure occurs, the connection description is not stored
Pseudo-connection to HFSQL Classic database
Differences between HOpenConnection and HDescribeConnection
UDL file (file for describing an OLE DB connection)
Native Oracle Connector: managing the external authentication
Limitations

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

HOpenConnection (Function)

In french: HOuvreConnexion

Not available with this kind of connection

Opens a connection to a specific database. The connection remains opened until the call to HCloseConnection. HOpenConnection is used to:

open a preset connection.
define and open a connection. Then, this connection must be assigned to a data file with HChangeConnection.
define and open a connection by using a connection string. This syntax can be used with some OLE DB providers who have specific ADO connecting strings.

Access by JDBC: This option is not available.
open a connection defined by a Connection variable.

Caution: The order in which the functions for connecting to an HFSQL Client/Server database are called is important. For more details, see Optimizing the connection times to the HFSQL Client/Server databases.

Example

See additional examples

MyConnection is Connection
// Describe the connection
MyConnection.User = "USER"
MyConnection.Password = "PASSWORD"
MyConnection.Server = "MYSERVER"
MyConnection.Database = "Database"
MyConnection.Provider = hAccessHFClientServer
MyConnection.Access = hOReadWrite
MyConnection.ExtendedInfo = "Extended information"
MyConnection.CursorOptions = hClientCursor
HOpenConnection(MyConnection)

Syntax

Opening a preset connection Hide the details

<Result> = HOpenConnection(<Connection>)

<Result>: Boolean

True if the operation was performed,
False if a problem occurred (during a connection described through programming, some parameters used in HDescribeConnection may be incorrect for example).
HErrorInfo is used to identify the error.

<Connection>: Character string or Connection variable

Connection to a database. This connection corresponds to:
the name of the connection defined in the data model editor,
the name of the connection defined by HDescribeConnection. The connection description must be known when running the function.
the name of a variable of type Connection.

Defining and opening a connection Hide the details

<Result> = HOpenConnection(<New connection> , <User> [, <Password>] , <Data source> [, <Database>] , <OLE DB provider or Native Connector> [, <Access> [, <Extended information> [, <Additional options>]]])

<Result>: Boolean

True if the operation was performed,
False if a problem occurs. HErrorInfo is used to identify the error. To assign this connection to a file, use HChangeConnection. The connection description will be deleted when closing the connection.

<New connection>: Character string or Connection variable

Name of new connection to define and to open. This name must not be used by another connection (defined in the analysis, or by HOpenConnection or HDescribeConnection).
This parameter corresponds to the Name property used on a variable of type Connection.

<User>: Character string

Username used for the database. This parameter can be modified and retrieved using the User property on a variable of type Connection.

<Password>: Optional character string

Connection password (if this password exists). If no password is required, use an empty string ("") or the NULL keyword. This parameter can be modified using the Password property on a variable of type Connection.

<Data source>: Character string

Full path of the data source. The connection will be created and opened for this data source.
This parameter can be retrieved and modified using the Source property (or Server) on a variable of type Connection.
This parameter corresponds to the server name. The port number used by the HFSQL server can be specified. The port 4900 will be used by default. If the port number of the HFSQL server is different, use the following notation:
<Computer name>: <Port number>
Example: "ComputerName:4901".
For a use via Internet, the ports must be managed by Firewall. For more details, see Managing ports. You have the ability to specify an IPv6 address by writing the IPv6 address between square brackets. In this case, the port number must be specified after the closing square bracket. For example: [0154:2145:2155::5554]:4900.
Access by JDBC:
This parameter must correspond to URL of the connection to the database. This URL is specific to each driver.
Depending on the JDBC driver used, the database name must be specified in the connection URL.

<Database>: Optional character string

Name of database that will be used on the data source. If this parameter is not required, use an empty string ("").
This parameter can be retrieved and modified using the Database property on a variable of type Connection.
In the case of a database divided into schemas, the name of the schema in the database will be specified by HChangeName.
This database will be automatically created if it does not exist.
DB2: This parameter is not required.

<OLE DB provider or Native Connector>: Character string or constant

Name of OLE DB provider used. To easily retrieve the string to use, select "Connection" in the data model editor (see the Notes).
or
one of the following constants:
hAccessHF7 Pseudo-connection to HFSQL Classic database.
hAccessHFClientServer Native Connector to an HFSQL Client/Server database.
hNativeAccessAS400 Native AS/400 Connector (optional module of WINDEV/WEBDEV).
hNativeAccessDB2 Native DB2 Connector (optional module of WINDEV/WEBDEV).
hNativeAccessInformix Native Informix Connector (optional module of WINDEV/WEBDEV).
hNativeAccessMariaDB Native MariaDB Connector (optional module of WINDEV/WEBDEV).
hNativeAccessMySQL Native MySQL Connector (optional module of WINDEV/WEBDEV).
hNativeAccessOracle Native Oracle Connector (optional module of WINDEV/WEBDEV).
hNativeAccessOracleLite Native Oracle Connector (optional module of WINDEV Mobile).
hNativeAccessPostgreSQL Native PostgreSQL Connector (optional module of WINDEV/WEBDEV).
hNativeAccessProgress Native Progress Connector (optional module of WINDEV/WEBDEV).
hNativeAccessSQLAzure Native SQL Azure Connector (optional module of WINDEV/WEBDEV, supplied with Native SQL Server Connector).
hNativeAccessSQLite Native SQLite Connector (provided with WINDEV/WEBDEV).
hNativeAccessSQLServer Native SQL Server Connector (optional module of WINDEV/WEBDEV)
The former Native Connector is used by default. To use the new Native SQL Server Connector, use the H.SQLServerMode variable.
hNativeAccessSQLServerMobile Native SQL Server Mobile Connector (optional module of WINDEV Mobile).
hNativeAccessSybase Native Sybase Connector (optional module of WINDEV/WEBDEV).
hNativeAccessXBase Native xBase Connector (provided with WINDEV/WEBDEV).
hNativeAccessXML Native XML Connector (supplied with WINDEV/WEBDEV).
hODBC OLE DB provider for ODBC (used to access an ODBC data source declared in the ODBC data sources of Windows).
hOledbAccess97 OLE DB provider for Access 97.
hOledbAccess2000 OLE DB provider for Access 2000.
hOledbAccess2007 OLE DB provider for Access 2007.
hOledbAccess2010 OLE DB provider for Access 2010.
hOledbDBase5 OLE DB provider for dBase 5.
hOledbExcel97 OLE DB provider for Excel 97.
hOledbExcel2000 OLE DB provider for Excel 2000.
hOledbExcel2007 OLE DB provider for Excel 2007.
hOledbLotus4 OLE DB provider for Lotus 4.
hOledbOracle OLE DB provider for Oracle.
hOledbSQLServer OLE DB provider for SQL Server

The available constants are as follows:
hAccessHF7 Pseudo-connection to an HFSQL database
hAccessHFClientServer Connection to an HFSQL Client/Server database.
hAccessJDBCMySQL Access to MySQL database via JDBC.
hAccessJDBCSQLite Access to SQLite database via JDBC.
hAccessJDBCSQLServer Access to SQL Server database via JDBC.

Caution: To use an OLE DB connection, you must:
install MDAC version 2.6 or later (setup performed by WINDEV/WEBDEV and when creating the client version).
install the OLE DB provider corresponding to the database used.
This parameter is returned by the CtOLEDBProvider property.
This parameter can be retrieved and modified using the Provider property on a variable of type Connection.

<Access>: Optional constant

Configures the type of access to the database.
hORead The database can be accessed in read-only. You can only read records. No record can be added or deleted.
This constant is ignored.
hOReadWrite
(default value) The database can be accessed in read/write. You can read and write new records.
This parameter can be retrieved and modified using the Access property on a variable of type Connection.
Access by JDBC: This parameter is ignored.

<Extended information>: Optional character string

Optional information inserted into the string for connecting to the database. If specific keywords are recognized, the corresponding information is extracted from the connection string. The rest of the connection string is sent to the database. Then, the extracted parameters are processed by the Native Connector or by the OLE DB connector used.
These keywords must be indicated as follows: "<Keyword> = <Value>;".
You can for example specify "Trusted_Connection=YES" in order to use a connection with authentication via the NT login.
The keywords recognized by OLE DB and the Native Connectors are displayed on Optional connection information.
Example of string to use:
"WD Cache Size = 10000; Server Port=3306;"

Recognized keywords for the access via HFSQL Client/Server:
COMPRESSION Enables or disables the compression of data exchanged between Client and Server. This keyword can correspond to:
TRUE to enable the data compression.
FALSE to disable the data compression.
DB_EXIST Checks the existence of the database. If the specified database does not exist, this database is not created and HOpenConnection returns False.
ENCRYPTION Enables the encryption of data exchanged between Client and Server. This keyword can take one of these values:
FAST
RC5_16 to use 16-round RC5 encryption.
AES128 to use 128-bit AES encryption with the OFB mode of operation.
AES192 to use 192-bit AES encryption with the OFB mode of operation.
AES256 to use 256-bit AES encryption with the OFB mode of operation.

This parameter can be retrieved and modified using the ExtendedInfo property.
HFSQL database accessed via a RMI server: This parameter corresponds to the address of RMI server and to the port used. The following format must be used: "RMI=<Server address>:<Port number>". For example: "RMI=192.168.52.148:1099".
Access by JDBC: This parameter is mandatory. It must correspond to the full name of JDBC driver to use. This name is case sensitive.

<Additional options>: Optional constant

If this parameter is not specified, the HFSQL engine automatically defines the best parameters to use according to the database accessed and to the OLE DB provider used.
By default, this parameter corresponds to the following combination of constants:
hServerCursor + hOpenKeysetCursor + hOptimisticCursor
However, these parameters can differ according to the information returned by the database.
To force some parameters, you have the ability to combine the following constants:
Location of cursors
hClientCursor Cursor managed by MDAC. Offers more features than a server cursor. A client cursor must necessarily be a static cursor.
hServerCursor Cursor managed by the database. This cursor can easily apply the changes performed by the other users to the data.
Type of cursor
hDynamicCursor Cursor offering a lot of features but consuming a lot of memory. This cursor allows all types of moves. It allows you to access all the modifications, additions and deletions performed by the other users.
hForwardOnlyCursor Fast cursor consuming little memory. The move is performed from the first record to the last one. The data modified by the other users is not visible.
hOpenKeysetCursor Cursor that handles a fixed set of records. Only the keys corresponding to the record are stored and not the records (consumes less memory). The deleted records can no longer be accessed. Modifications performed by other users are visible (but records added are not).
hStaticCursor Makes a copy of all query records in memory (high memory usage). All types of moves are allowed.
Lock mode
hOptimisticCursor The record is locked when it is updated
hPessimisticCursor The record is locked as soon as it goes into edit mode to be modified.
hReadOnlyCursor The set of records cannot be modified.
Caution: some types of cursors may not be supported by all the OLE DB providers.
This parameter can be retrieved and modified using the CursorOptions property.

Defining and opening a connection by defining the connection string Hide the details

<Result> = HOpenConnection(<Connection> , <ADO connection string> [, <Access>])

<Result>: Boolean

True if the operation was performed,
False if a problem occurs. HErrorInfo is used to identify the error. The connection description will be deleted when closing the connection.

<Connection>: Character string

Name of new connection to define and to open. This name must not be used by another connection (defined in the analysis, or by HOpenConnection or HDescribeConnection).

<ADO connection string>: Character string

ADO connection string to use. For more details on the syntax of this connection string, see the documentation of the OLE DB provider used.

<Access>: Optional constant

Configures the type of access to the database.
hORead The database can be accessed in read-only. You can only read records. No record can be added or deleted.
hOReadWrite
(default value) The database can be accessed in read/write. You can read and write new records.

Remarks

Syntax 1: Opening a preset connection: automatic management of connections

The connection associated with a data file is automatically opened when the data file is opened. The connection is closed when the last data file that uses this connection is closed.
Any connection opened by HOpenConnection remains open even if no data file uses it.
If the application opens and closes data files many times in a row, the automatic management of connections will open/close connections many times, slowing down the application. In this case, it is recommended to use HOpenConnection to keep the connection open.

Syntax 2: Using a character string for the OLE DB provider

To easily find the character string that must be used to define the OLE DB provider, we recommend that you proceed as follows:

In the analysis editor, create an HFSQL Client/Server connection, for example.
In the connection description screen, select the provider to be used (in "Connection by").
The character string corresponding to the provider is displayed. This character string can be used in the syntax 2 instead of constants.

Using a character string for the OLE DB provider

Syntax 2 and 3: If a failure occurs, the connection description is not stored

If the connection fails to open, the description of this connection is not validated. This allows you to redefine a connection with the same name.

For example, if the attempt to connect with the default password fails, you have the ability to perform a new attempt with another password.

Pseudo-connection to HFSQL Classic database

OLE DB data files or native data files are described in the data model editor. To handle these descriptions with an HFSQL Classic database, simply specify the hAccessHF7 constant as provider name.

The data files in HFSQL Classic format corresponding to the description of the OLE DB or native files will be created (if necessary) in the directory defined by <Data source>.

Differences between HOpenConnection and HDescribeConnection

Method 1: To open a connection at the start of the application and close it at the end, use HOpenConnection. To use this connection when handling data files or tables, simply change this connection with HChangeConnection.

HOpenConnection(MyConnection, params) // Open the connection
HChangeConnection(AFile, MyConnection)

Method 2: To describe a connection through programming and to automatically open it when the file is opened, you must:

describe the connection with HDescribeConnection
associate this connection with the desired data file description using HChangeConnection. The connection will only be opened the first time the data file is accessed.

This solution can be useful when an application handles both HFSQL data files and Oracle data files. For example, if the application uses a single Oracle file, in a specific process, the connection to the Oracle database will only be made if necessary.

If the first solution is chosen for the same type of application, the connection (that may take quite a long time) will be established whenever the application is started.

Example:

HDescribeConnection(MyConnection, params)
HChangeConnection(AFile, MyConnection)
...
HReadFirst(AFile) // Open the connection
...
HClose(AFile) // Close the connection

UDL file (file for describing an OLE DB connection)

To create a UDL file:

Create a text file whose extension is "UDL".
Double-click this file. The window for the properties of the data links is opened.
Configure the connection.
Run the test of the connection.
Confirm ("OK" button). The UDL file can now be used.

Native Oracle Connector: managing the external authentication

To connect via an external authentication, the following connection parameters must be used:

<Username> = / (slash)
<Password> = "" (empty string)

Remark: The external authentication consists in using the name of Windows user and his password to connect to the database. The external authentication requires configuring the server. See the Oracle documentation to learn more about how to authorize external authentications on the server.

Limitations

Component: wd300hf.dll