Data Access Controls

The Data Access tab provides 9 database components for connecting to local and remote databases. All components share a common interface for connection management and query execution.

Common Properties

All database components (except TDBFTable) share these connection properties:

Property	Type	Default	Description
cHost	String	"localhost"	Database server hostname or IP address
nPort	Numeric	varies	Server port (driver-specific default)
cDatabase	String	""	Database name
cUser	String	""	Authentication username
cPassword	String	""	Authentication password
lConnected	Logical	.F.	Current connection status (read-only)
lAutoConnect	Logical	.F.	Automatically connect when the form is activated
cCharset	String	"UTF8"	Character set for the connection

Common Events

Event	Category	Description
OnConnect	Connection	Successfully connected to the database
OnDisconnect	Connection	Disconnected from the database
OnError	Error	Connection or query error. Params: nCode, cMessage
OnBeforeQuery	Query	Fired before a query executes. Params: cSQL. Return .F. to cancel
OnAfterQuery	Query	Fired after a query completes. Params: oResultSet, nRows

Common Methods

Method	Description
Connect()	Open a connection to the database server
Disconnect()	Close the connection
Execute( cSQL )	Execute a SQL statement (INSERT, UPDATE, DELETE). Returns nAffectedRows
Query( cSQL )	Execute a SELECT query. Returns an oResultSet object
BeginTrans()	Start a transaction
Commit()	Commit the current transaction
Rollback()	Roll back the current transaction

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TDBFTable CT_DBFTABLE = 53

Native xBase DBF table access. Provides direct access to DBF/NTX/CDX files without a server. The classic Harbour/Clipper data format.

Property	Type	Default	Description
cFile	String	""	Path to the .dbf file
cAlias	String	""	Work area alias name
lShared	Logical	.T.	Open in shared mode (multi-user)
lReadOnly	Logical	.F.	Open as read-only
cDriver	String	"DBFCDX"	RDD driver (DBFCDX, DBFNTX, DBFNSX)

TSQLite CT_SQLITE = 54

SQLite embedded database. Zero-configuration, serverless, single-file database engine.

Property	Type	Default	Description
cFile	String	""	Path to the .db or .sqlite file
lInMemory	Logical	.F.	Use an in-memory database (no file)
lWAL	Logical	.T.	Enable Write-Ahead Logging for better concurrency
lForeignKeys	Logical	.T.	Enable foreign key constraint enforcement

TMySQL CT_MYSQL = 55

MySQL / MariaDB client connector. Default port: 3306.

Property	Type	Default	Description
nPort	Numeric	3306	Server port
lSSL	Logical	.F.	Use SSL/TLS connection
lCompress	Logical	.F.	Enable protocol compression

TPostgreSQL CT_POSTGRESQL = 56

PostgreSQL client connector. Default port: 5432.

Property	Type	Default	Description
nPort	Numeric	5432	Server port
cSchema	String	"public"	Default schema
lSSL	Logical	.F.	Use SSL/TLS connection

TFirebird CT_FIREBIRD = 57

Firebird SQL client connector. Default port: 3050.

Property	Type	Default	Description
nPort	Numeric	3050	Server port
cRole	String	""	SQL role name
nDialect	Numeric	3	SQL dialect (1 or 3)

TSQLServer CT_SQLSERVER = 58

Microsoft SQL Server client connector. Default port: 1433.

Property	Type	Default	Description
nPort	Numeric	1433	Server port
lTrustedAuth	Logical	.F.	Use Windows integrated authentication
cAppName	String	""	Application name for server monitoring

TOracle CT_ORACLE = 59

Oracle Database client connector. Default port: 1521.

Property	Type	Default	Description
nPort	Numeric	1521	Server port
cServiceName	String	""	Oracle service name (alternative to cDatabase)
cSchema	String	""	Default schema

TODBC CT_ODBC = 60

Generic ODBC connector. Connects to any database with an ODBC driver.

Property	Type	Default	Description
cDSN	String	""	ODBC Data Source Name
cConnString	String	""	Full ODBC connection string (overrides individual properties)

TADOConnection CT_ADO = 61

ADO (ActiveX Data Objects) connector. Windows-only. Connects to any OLE DB provider.

Property	Type	Default	Description
cProvider	String	""	OLE DB provider name
cConnString	String	""	Full ADO connection string

Platform	Availability
Windows	Full support via COM/OLE
macOS	Not available
Linux	Not available

Code Example: SQLite Database

// Connecting to an SQLite database and querying data

FUNCTION Main()

   LOCAL oDB, oRS

   // Create and configure the SQLite connection
   oDB := TSQLite():New()
   oDB:cFile := "myapp.db"
   oDB:lWAL  := .T.

   oDB:OnError := { |n, c| QOut( "DB Error: " + c ) }

   // Connect and create a table
   oDB:Connect()

   oDB:Execute( "CREATE TABLE IF NOT EXISTS customers (" + ;
               "  id INTEGER PRIMARY KEY AUTOINCREMENT,"  + ;
               "  name TEXT NOT NULL,"                    + ;
               "  email TEXT,"                             + ;
               "  city TEXT )" )

   // Insert some records
   oDB:Execute( "INSERT INTO customers (name, email, city) VALUES ('John', 'john@test.com', 'NYC')" )
   oDB:Execute( "INSERT INTO customers (name, email, city) VALUES ('Maria', 'maria@test.com', 'Madrid')" )

   // Query data
   oRS := oDB:Query( "SELECT * FROM customers ORDER BY name" )

   DO WHILE ! oRS:Eof()
      QOut( oRS:FieldGet( "name" ), oRS:FieldGet( "email" ) )
      oRS:MoveNext()
   ENDDO

   oRS:Close()
   oDB:Disconnect()

RETURN NIL