Class
ODBCDatabase
Description
Used to open an ODBC database using an ODBC drivers. You use the constants in the ODBCConstant module with the methods and properties of the ODBCDatabase class.
Properties
Name |
Type |
Read-Only |
Shared |
---|---|---|---|
✓ |
|||
Methods
Name |
Parameters |
Returns |
Shared |
---|---|---|---|
tableName As String, row As DatabaseRow |
|||
tableName As String, row As DatabaseRow, idColumnName As String = "" |
|||
Attribute As Integer |
|||
Attribute As Integer |
|||
DataType As Integer |
|||
command As String, ParamArray values() As Variant |
|||
statement As String |
|||
table As String |
|||
query As String, Paramarray values() As Variant |
|||
ProcedureName As String |
|||
tableName As String |
|||
tableName As String |
|||
table As String |
|||
identifierType As Integer, table As String, scope As Integer, nullable As Integer |
|||
Property descriptions
ODBCDatabase.Attribute
Attribute As Integer
Optional attribute. This property is used in conjunction with the AttributeString property to set a string property using the SQLSetConnectAttr ODBC API function.
Using the Attribute property, the attribute is only set before the connection is made to the database. Although the Attribute / AttributeString properties are readable, they are not updated with information from the database.
The AttributeString property is not passed to the database if the Attribute property is set to zero (the default).
For more information, see the documentation for the SQLSetConnectAttr function at msdn.microsoft.com.
If you don't want to use Attribute, pass zero.
The following code sets the SQL_CURRENT_QUALIFIER property:
db.Attribute = :doc:`ODBCConstant</api/databases/odbcconstant>`.SQL_CURRENT_QUALIFIER
db.AttributeString = "NorthWind"
ODBCDatabase.AttributeString
AttributeString As String
Optional attribute. This property is used in conjunction with the Attribute property to set a string property using the SQLSetConnectAttr ODBC API function.
Using the Attribute property, the attribute is only set before the connection is made to the database. Although the Attribute / AttributeString properties are readable, they are not updated with information from the database.
The AttributeString property is not passed to the database if the Attribute property is set to zero (the default).
For more information, see the documentation for the SQLSetConnectAttr function at msdn.microsoft.com.
If you don't want to pass AttributeString, pass the empty string.
The following code sets the SQL_CURRENT_QUALIFIER property:
db.Attribute = :doc:`ODBCConstant</api/databases/odbcconstant>`.SQL_CURRENT_QUALIFIER
db.AttributeString = "NorthWind"
ODBCDatabase.DatabaseName
DatabaseName As String
The name of the database to open.
The DatabaseName is typically used to identify the specific database to use on the server.
This code connects to a database called "BaseballLeague":
Var db As New ODBCDatabase
db.Host = "192.168.1.172"
db.Port = 5432
db.DatabaseName = "BaseballLeague"
db.UserName = "broberts"
db.Password = "streborb"
Try
db.Connect
' Use the database
Catch error As DatabaseException
' DB Connection error
MessageBox(error.Message)
End Try
ODBCDatabase.DataSource
DataSource As String
The connection string to be used to establish a connection to an ODBC database. The connection string can either contain only the DSN name, or a string containing one or more keywords defined for the driver.
If only the DSN is passed, then the UserName and Password properties are used for the connection. If the connection string contains keywords, then the UserName and Password properties are ignored. See your driver documentation for information about which keywords are supported.
Pass an empty string ("") to the DataSource property to get an open-file dialog box. It will prompt you to choose a list of defined DSNs. The DataSource property may be updated by the ODBC driver with additional parameters used after a connection is made.
For examples of connection strings for various databases, visit http://www.connectionstrings.com.
This example prompts the user to select a Data Source:
Var db As New ODBCDatabase
db.DataSource = ""
Try
db.Connect
' proceed with database operations
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
End Try
This example specifies the DSN information to connect to a Microsoft Access database:
Var db As New ODBCDatabase
db.DataSource = "Driver={Microsoft Access Driver (*.mdb)};Dbq=C:\TestAccessDB.mdb;Uid=Admin;Pwd=;"
Try
db.Connect
' proceed with database operations
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
End Try
ODBCDatabase.DBMS
DBMS As String
This property returns the type of the connected database, such as MySQL or Oracle. The property only contains a value after a successful connection has been made to the database. Writing to the property has no effect.
This property is read-only.
This property is equivalent to calling the GetInfo method with the ODBCConstant.SQL_DBMS_NAME.
After connecting to a database with ODBC, you can display its type:
MessageBox("DB Type: " + db.DBMS)
ODBCDatabase.IsExtendedSchema
IsExtendedSchema As Boolean
When set to True, additional columns are returned for FieldSchema and TableSchema.
Additional columns are described below
For FieldSchema:
TableName
NonUnique
IndexQualifier
Type
OrdinalPosition
ColumnName
TableCatalog
TableSchema
AscOrDesc
Cardinality
Pages
FilterCondition
For TableSchema:
TableType
Remarks
TableCatalog
TableSchema
ODBCDatabase.IsScrollableCursor
IsScrollableCursor As Boolean
This property can be set to True in order to cause cursors opened using SQLSelect to be “scrollable.” A RowSet with a scrollable cursor can be navigated in both the forward and backward directions (i.e., using MoveToPreviousRow in addition to MoveToNextRow). The default behavior is for a cursor to be non-scrollable (forward only). This property only has an effect if supported by the underlying ODBC driver.
ODBCDatabase.Host
Host As String
The database host name or IP address of the database server.
This examples connects to a database called "BaseballLeague":
Var db As New ODBCDatabase
db.Host = "192.168.1.172"
db.Port = 5432
db.DatabaseName = "BaseballLeague"
db.UserName = "broberts"
db.Password = "streborb"
Try
db.Connect
' Use the database
Catch error As DatabaseException
' DB Connection error
MessageBox(error.Message)
End Try
ODBCDatabase.Password
Password As String
The password that is required for access to the database. Typically used in conjunction with UserName.
This examples connects to a database called "BaseballLeague":
Var db As New ODBCDatabase
db.Host = "192.168.1.172"
db.Port = 5432
db.DatabaseName = "BaseballLeague"
db.UserName = "broberts"
db.Password = "streborb"
Try
db.Connect
' Use the database
Catch error As DatabaseException
' DB Connection error
MessageBox(error.Message)
End Try
ODBCDatabase.Timeout
Timeout As Integer
The timeout value (in seconds) to be used when connecting to the database. The default is 0, which will use the ODBC driver value.
The timeout value is set before actually connecting to the database. The property can be read, but the value that was previously set will be returned. The value is not returned from the driver. To get the actual value from the driver, use the ConnectionAttribute method with the ODBCConstant.SQL_LOGIN_TIMEOUT parameter.
Set the timeout to 60 seconds:
' db is an existing ODBCDatabase connection
db.Timeout = 60
ODBCDatabase.UserName
UserName As String
The username that is required for access to the database.
This code connects to a database called "BaseballLeague":
Var db As New ODBCDatabase
db.Host = "192.168.1.172"
db.Port = 5432
db.DatabaseName = "BaseballLeague"
db.UserName = "broberts"
db.Password = "streborb"
Try
db.Connect
' Use the database
Catch error As DatabaseException
' DB Connection error
MessageBox(error.Message)
End Try
Method descriptions
ODBCDatabase.AddRow
AddRow(tableName As String, row As DatabaseRow)
Inserts row as a new row in TableName.
AddRow(tableName As String, row As DatabaseRow, idColumnName As String = "") As Integer
Inserts row as a new row in tableName returning the newly assigned ID in the idColumnName column.
Always look for a DatabaseException to verify whether or not the data was added.
This code adds a row to an existing Team table with the columns "Name", "Coach" and "City". It's assumed that the variable db contains an active database connection:
Var row As New DatabaseRow
' ID will be updated automatically
row.Column("Name") = "Penguins"
row.Column("Coach") = "Bob Roberts"
row.Column("City") = "Boston"
Try
db.AddRow("Team", row)
Catch error As DatabaseException
MessageBox("DB Error: " + error.Message)
End Try
ODBCDatabase.BeginTransaction
BeginTransaction
Creates a new transaction. Changes to the database made after this call can be saved with CommitTransaction or undone with RollbackTransaction.
A DatabaseException will be raised if the transaction could not begin or another transaction is already in progress.
You typically want to Commit changes after ensuring there were no database errors:
' Prior DB code has run
Try
DB.BeginTransaction
DB.ExecuteSQL("CREATE TABLE AddressBook name VARCHAR, email VARCHAR")
DB.CommitTransaction
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
DB.RollbackTransaction
End Try
ODBCDatabase.Close
Close
Closes or disconnects the database.
Calling Close does not issue a Commit, but some databases will automatically Commit changes in a transaction when you Close the connection and some database will automatically Rollback changes in a transaction when the connection is closed. Refer to the documentation for your database to check what its behavior is.
For desktop apps, you will often Connect to the database when the app starts and Close it when the app quits.
For web apps, you usually Connect to the database when the Session starts and Close it when the Session quits.
This code in the App.Closing event handler closes a previously connected database:
DB.Close ' DB is a property on App
ODBCDatabase.CommitTransaction
CommitTransaction
Commits an open transaction. This permanently saves changes to the database.
A DatabaseException will be raised if the transaction could not be committed.
You have to have an open transaction to be able to use CommitTransation. Use BeginTransaction to begin a transaction:
DB.BeginTransaction
You typically want to commit changes after ensuring there were no database errors:
' Prior DB code has run
Try
DB.CommitTransaction
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
DB.RollbackTransaction
End Try
ODBCDatabase.Connect
Connect
Connects to the database so that you can begin using it.
Warning
A DatabaseException will be raised if the connection could not be made.
This example connects to the database object in the variable db:
Try
db.Connect
MessageBox("Connected!")
Catch error As DatabaseException
MessageBox("Error connecting to the database: " + error.Message)
End Try
ODBCDatabase.ConnectionAttribute
ConnectionAttribute(Attribute As Integer) As Variant
Gets and sets the current setting of a connection attribute. Returns a Variant that contains either a String or an Integer, based on the attribute.
The attribute can be specified using the ODBCConstant constants. The value is only set after the connection is made. Only Integer attributes may be set with this method. To set a String attribute before the connection is made, see the Attribute property.
Microsoft provides additional information about the SQLGetConnectAttr ODBC function.
Obtaining an attribute:
Var currentCatalog As Variant
currentCatalog = db.ConnectionAttribute(ODBCConstant.SQL_CURRENT_QUALIFIER)
Setting an attribute to disable AutoCommit:
db.ConnectionAttribute(ODBCConstant.SQL_AUTOCOMMIT) = ODBCConstant.SQL_AUTOCOMMIT_OFF
ODBCDatabase.ConnectionInfo
ConnectionInfo(Attribute As Integer) As Variant
Returns general information about the driver and data source associated with a connection. Returns a Variant that contains either a String or an Integer, based on the attribute.
ODBCConstant contains integer values that you can use with this function.
Microsoft provides additional information about the SQLGetInfo ODBC function.
Check if the connected ODBC database supports stored procedures:
'db is a valid database connection
Try
db.Connect
MessageBox(db.ConnectionInfo(ODBCConstant.SQL_PROCEDURES))
Catch error As DatabaseException
MessageBox("Error: " + error.ErrorMessage)
End Try
ODBCDatabase.DataSources
DataSources As RowSet
Returns a RowSet with a list of configured Data Source Names (DSN). Returns both User and System DSNs in a single RowSet.
The instance of the ODBCDatabase does not have to be connected to a database in order to use this method.
The RowSet returned by DataSources has two columns. They are:
Name: The data source name
Description: The Name of the ODBC driver.
Microsoft provides additional information about the SQLDataSources ODBC function.
This code gets all the ODBC data source names and adds them to a ListBox:
DataSourceList.DeleteAllRows
Var rs As RowSet
rs = db.DataSources
If rs <> Nil Then
While Not rs.AfterLastRow
DataSourceList.AddRow(rs.Column("Name").StringValue, rs.Column("Description").StringValue)
rs.MoveToNextRow
Wend
rs.Close
End If
ODBCDatabase.DataTypeInfo
DataTypeInfo(DataType As Integer) As RowSet
Returns a RowSet containing information about data types supported by the data source.
The DataType specifies the type for which the information should be returned.
Use ODBCConstant values for the data types.
To return a RowSet containing all defined types, specify ODBCConstant.SQL_ALL_TYPES.
The returned RowSet typically contains these columns, but they could vary depending on the driver being used:
Data Type Name
Data Type integer value
Column size
Microsoft provides additional information about the SQLGetTypeInfo ODBC function.
Displays all the supported data types for the current ODBC connection in a ListBox:
'Var db is a valid database connection
db.DataSource = "TeamExample"
Try
db.Connect
Var rs As RowSet
rs = db.DataTypeInfo(ODBCConstant.SQL_ALL_TYPES)
If rs <> Nil Then
For Each row As DatabaseRow In rs
ListBox1.AddRow(rs.ColumnAt(0).StringValue)
Next
End If
Catch error As DatabaseException
MessageBox("Connection failed. Error:" + error.ErrorMessage)
End Try
ODBCDatabase.Drivers
Drivers As RowSet
Returns a RowSet with a list of configured ODBC drivers.
The instance of the ODBCDatabase does not have to be connected to a database in order to use this method.
The RowSet returned by DataSources has two columns. They are:
Name: The driver name
Description: A description indicating if the driver is installed
Type: The type (for example, System).
Microsoft provides additional information about the SQLDrivers ODBC function.
ODBCDatabase.ExecuteSQL
ExecuteSQL(command As String, ParamArray values() As Variant)
Used to execute an SQL command. Use this for commands that do not return any data, such as CREATE TABLE
or INSERT
. The command parameter contains the SQL statement.
Tip
You can also pass an array of values as the first and only parameter instead of a ParamArray.
Warning
A DatabaseException will be raised if the SQL passed is invalid or if an error occurs.
Passing values as parameters protects your database by automatically creating a ODBCPreparedStatement.
In this example, the database is being updated without the use of parameters and thus leaves the database vulnerable to a SQL injection attack:
' Updates a table in a database (db)
Var sql As String
sql = "UPDATE Customer SET City='" + CityField.Text + "' WHERE PostalCode='" + PostalCodeField.Text + "'"
Try
db.ExecuteSQL(sql)
Catch error As DatabaseException
MessageBox("DB Error: " + error.Message)
End Try
Here's the same example but using parameters which protects you against a SQL injection attack:
' Updates a table in a database (db)
Var sql As String
sql = "UPDATE Customer SET City=? WHERE PostalCode=?"
Try
db.ExecuteSQL(sql, CityField.Text, PostalCode.Text)
Catch error As DatabaseException
MessageBox("DB Error: " + error.Message)
End Try
The parameter values can also be passed in as a variant array:
Var sql As String
sql = "UPDATE Customer SET City=? WHERE PostalCode=?"
Var values(1) As Variant
values(0) = CityField.Text
values(1) = PostalCode.Text
Try
db.ExecuteSQL(sql, values)
Catch error As DatabaseException
MessageBox("DB Error: " + error.Message)
End Try
This code creates the Team table:
' db is a database
Var sql As String
sql = "CREATE TABLE Team (ID INTEGER NOT NULL, Name TEXT, Coach TEXT, City TEXT, PRIMARY KEY(ID));"
Try
db.ExecuteSQL(sql)
MessageBox("Team table created successfully.")
Catch error As DatabaseException
MessageBox("DB Error: " + error.Message)
End Try
ODBCDatabase.IsConnected
IsConnected As Boolean
Returns True if the connection to the database is still active.
ODBCDatabase.NextRowSet
NextRowSet As Boolean
Determines whether more results are available on a statement containing SELECT, UPDATE, INSERT, or DELETE statements and, if so, initializes processing for those results. This method only affects the most recently opened RowSet. Not all drivers support multiple RowSets. Returns True if another RowSet is available. You must execute MoveToNextRow on the previous RowSet to advance to the start of the next RowSet after calling NextRowSet.
For a command that can return multiple record sets from the ODBC database and driver, you iterate though each of them using the RowSet class. When you reach the end of a record set, use MoveToNextRow to initialize the next ODBC record set for processing by the RowSet class.
' db is a connected database
' rs contains multiple RowSets from the ODBC database
' First RowSet
While Not rs.AfterLastRow
' Process data in 1st record set
rs.MoveToNextRow
Wend
If db.NextRowSet Then ' Initialize next ODBC record set (if one is available)
While Not rs.AfterLastRow
' Process data in 2nd record set
rs.MoveToNextRow
Wend
End If
ODBCDatabase.Prepare
Prepare(statement As String) As PreparedSQLStatement
Creates a PreparedSQLStatement using the SQL statement for use with the ODBCPreparedStatement class. A prepared statement is an SQL statement with parameters that has been pre-processed by the database so that it can be executed more quickly if it is re-used with different parameters. Prepared statements also mitigate the risk of SQL injection in web apps.
If the provided SQL statement has an error, a DatabaseException will occur when you call SelectSQL or ExecuteSQL.
SQL Injection is a way to attack database-driven applications.
To create a prepared statement, you use the appropriate class for the database you are using. For example, to create a prepared statement for an ODBC database:
' db is a previously connected ODBCDatabase object
Var ps As ODBCPreparedStatement
ps = db.Prepare("SELECT * FROM Country WHERE code = $1")
ODBCDatabase.Privileges
Privileges(table As String, ColumnName As String) As RowSet
Returns a RowSet with a list of columns and associated privileges for the specified table.
Privileges(table As String, column As String ) As RowSet
Returns a RowSet with a list of associated privileges for the specified column.
If the database supports multiple catalogs and schemas, then the RowSet will contain records for all catalogs and schemas that can be accessed by the logged in user that match the given table name.
The column is a search pattern for a column name of the given table. Use an empty string to match all columns in the table.
Microsoft provides additional information regarding ODBC column privileges.
ODBCDatabase.StoredProcedureColumns
StoredProcedureColumns(ProcedureName As String) As RowSet
Returns a RowSet containing a list of columns associated with a given procedure stored in the database.
Not supported by all ODBC drivers.
Microsoft provides additional information about the SQLProcedureColumns ODBC function.
ODBCDatabase.RollbackTransaction
RollbackTransaction
Cancels an open transaction restoring the database to the state it was in before the transaction began.
A DatabaseException will be raised if the rollback could not be completed.
You will generally want to rollback database changes if a DatabaseException occurs within the transaction.
Important
While rolling back a transaction restores the database to its previous state, it has no impact on the data you access in a RowSet. To update the RowSet so that its data matches the database, you will need to re-query the database to recreate the RowSet.
You have to have an open transaction to be able to use Rollback. Call BeginTransaction to begin a transaction:
DB.BeginTransaction
This code uses rollback to revert database changes in a transaction when an error occurs:
' Prior DB code has run
Try
db.CommitTransaction
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
db.RollbackTransaction
End If
ODBCDatabase.SelectSQL
SelectSQL(query As String, ParamArray values() As Variant) As RowSet
Executes a SQL SELECT
statement and returns the results in a RowSet. The query parameter contains the SQL statement.
Tip
You can also pass an array of values as the first and only parameter instead of a ParamArray.
Warning
A DatabaseException will be raised if the SQL passed is invalid or if an error occurs.
Passing values as parameters protects your database by automatically creating a ODBCPreparedStatement.
This sample adds the names of all customers in a particular postal code to a ListBox. It passes the entire SQL select as a single statement and appends the value from a TextField called PostalCode, leaving the database vulnerable to a SQL injection attack:
' db is a valid connection to a database
Var rowsFound As RowSet
Try
rowsFound = db.SelectSQL("SELECT * FROM Customer WHERE PostalCode=" + PostalCode.Text)
For Each row As DatabaseRow In rowsFound
ListBox1.AddRow(row.Column("Name").StringValue)
Next
rowsFound.Close
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
End Try
This is the same code as above but instead it uses a value identifier (?) and then passes the value in separately to avoid a SQL injection attack:
' db is a valid connection to a database
Var rowsFound As RowSet
Try
rowsFound = db.SelectSQL("SELECT * FROM Customer WHERE PostalCode=?", PostalCode.Text)
For Each row As DatabaseRow In rowsFound
ListBox1.AddRow(row.Column("Name").StringValue)
Next
rowsFound.Close
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
End Try
Multiple values can be passed to SelectSQL. In this example, Age and PostalCode are both DesktopTextField controls:
' db is a valid connection to a database
Var rowsFound As RowSet
Try
rowsFound = db.SelectSQL("SELECT * FROM Customer WHERE Age=? AND PostalCode=?", Age.Value, PostalCode.Text)
For Each row As DatabaseRow In rowsFound
ListBox1.AddRow(row.Column("Name").StringValue)
Next
rowsFound.Close
Catch error As DatabaseException
MessageBox("Error: " + error.Message)
End Try
ODBCDatabase.StoredProcedures
StoredProcedures As RowSet
Returns a RowSet containing the names of the stored procedures in the database.
ODBCDatabase.TableColumns
TableColumns(tableName As String) As RowSet
Returns a RowSet with information about all the columns (fields) in the specified tableName.
Note
If an error occurs, a DatabaseException will be raised.
TableColumns returns a RowSet with these columns:
ColumnName: A string that is the name of the column.
FieldType: An integer that describes the type of the column (refer to the table below).
IsPrimary: A boolean that indicates if the column is part of the primary key.
NotNull: A boolean that indicates if the column can be set to NULL.
Length: An integer that describes the length of the field (for some text fields), the precision of numeric data (for some numeric fields) or the default value for a field (for SQLite columns).
cid: (SQLite Only) The ID of the column.
ODBC Databases may return different columns depending upon the database to which you are connecting.
This table identifies the Column Type based on the FieldType Integer:
Field Type |
Value |
Description |
---|---|---|
Null |
0 |
Denotes the absence of any value, i.e., a missing value. |
Byte |
1 |
Stores the byte representation of a character string. |
SmallInt |
2 |
A numeric data type with no fractional part. The maximum number of digits is implementation-specific, but is usually less than or equal to INTEGER. SQLite supports 4-byte smallints. If you are using another data source, check the documentation of your data source. |
Integer |
3 |
A numeric data type with no fractional part. The maximum number of digits is implementation-specific. SQLite supports 8-byte integer columns and the FieldType evaluates to 19 (64-bit integer). |
Char |
4 |
Stores alphabetic data, in which you specify the maximum number of characters for the field, i.e., CHAR (20) for a 20 character field. If a record contains fewer than the maximum number of characters for the field, the remaining characters will be padded with blanks. |
Text or VarChar |
5 |
Stores alphabetic data, in which the number of characters vary from record to record, but you don't want to pad the unused characters with blanks. For example, VARCHAR (20) specifies a VARCHAR field with a maximum length of 20 characters. |
Float |
6 |
Stores floating-point numeric values with a precision that you specify, i.e., FLOAT (5). |
Double |
7 |
Stores double-precision floating-point numbers. |
Date |
8 |
Stores year, month, and day values of a date in the format YYYY-MM-DD. The year value is four digits; the month and day values are two digits. |
Time |
9 |
Stores hour, minute, and second values of a time in the format HH:MM:SS. The hours and minutes are two digits. The seconds values is also two digits, may include a optional fractional part, e.g., 09:55:25.248. The default length of the fractional part is zero. |
TimeStamp |
10 |
Stores both date and time information in the format YYYY-MM-DD HH:MM:SS. The lengths of the components of a TimeStamp are the same as for Time and Date, except that the default length of the fractional part of the time component is six digits rather than zero. If a TimeStamp values has no fractional component, then its length is 19 digits If it has a fractional component, its length is 20 digits, plus the length of the fractional component. |
Currency |
11 |
This is a 64-bit fixed-point number format that holds 15 digits to the left of the decimal point and 4 digits to the right. |
Boolean |
12 |
Stores the values of TRUE or FALSE. |
Decimal |
13 |
Stores a numeric value that can have both an integral and fractional part. You specify the total number of digits and the number of digits to the right of the decimal place, i.e., DECIMAL (5.2) specifies a decimal field that can contain values up to 999.99. DECIMAL (5) specifies a field that can contain values up to 99,999. |
Binary |
14 |
Stores code, images, and hexadecimal data. Consult the documentation of your data source for information on the maximum size of a Binary field. |
Long Text (Blob) |
15 |
Stores a text object. Consult the documentation of your data source for information on the maximum size of a Blob. |
Long VarBinary (Blob) |
16 |
Stores a binary object. SQLite supports blobs of up to any size. Furthermore, a blob can be stored in a column of any declared data affinity. If you are using another data source, check the documentation of your data source. |
MacPICT |
17 |
Stores a Macintosh PICT image. SQLite does not support this data type. Use a Blob to store images. |
String |
18 |
Text up to about 2 billion bytes. The same as VarChar. |
Int64 |
19 |
Stores a 64-bit integer. Integer fields in SQLite are 64 bits and FieldType returns 19. |
Unknown |
255 |
Unrecognized data type. |
Note
Depending upon the version you are using, only a subset of these types may be supported.
The following code creates a table and then display each column name one at a time:
'db is a valid database connection'
Try
db.ExecuteSQL("CREATE TABLE Invoices (ID INTEGER, CustID INTEGER, Amount Double, Note TEXT)")
Var columns As RowSet = db.TableColumns("Invoices")
For Each c As DatabaseRow In columns
MessageBox("Column: " + c.Column("ColumnName").StringValue)
Next
Catch error As IOException
MessageBox("The database could not be created: " + error.Message)
Catch error As DatabaseException
MessageBox("Database error: " + error.Message)
End Try
ODBCDatabase.TableIndexes
TableIndexes(tableName As String) As RowSet
Returns a RowSet containing the list of indexes for the passed tableName. Returns Nil if the table has no indexes or the database source does not support indexes.
A DatabaseException will be raised if an error occurs.
The RowSet returns one row for each index on the table and it has one field: IndexName As String.
This code displays the indexes for the "Invoices" table (if it exists) in the specified database:
'db is a valid database connection
Try
db.Connect
Var indexRS As RowSet
indexRS = db.TableIndexes("Invoices") ' A table with indexes in the DB
For Each row As DatabaseRow In indexRS
MessageBox("Index: " + row.ColumnAt(0).StringValue)
Next
indexRS.Close
Catch error As NilObjectException
MessageBox("This database has no indexes.")
Catch error As DatabaseException
MessageBox("Could not connect to database. Error: " + error.Message)
End Try
ODBCDatabase.TableForeignKeys
TableForeignKeys(primaryTable As String, foreignTable As String) As RowSet
Returns a RowSet containing either a list of foreign keys in the specified table (columns in the specified table that refer to primary keys in other tables), or a list of foreign keys in other tables that refer to the primary key in the specified table.
Not all ODBC drivers support this feature. If it is not supported, it will return Nil.
Microsoft provides additional information about the SQLForeignKeys ODBC function.
ODBCDatabase.TablePrimaryKeys
TablePrimaryKeys(table As String) As RowSet
Returns a RowSet containing the column names that make up the primary key for a table.
Displays the primary keys for a table:
Var db As New ODBCDatabase
db.DataSource = "TeamExample"
If Not db.Connect Then
MessageBox("Error: " + db.ErrorMessage)
End If
Var rs As RowSet
rs = db.TablePrimaryKeys("Team")
If rs <> Nil Then
While Not rs.AfterLastRow
ListBox1.AddRow(rs.ColumnAt(1).StringValue)
rs.MoveToNextRow
Wend
rs.Close
End If
ODBCDatabase.TableSpecialColumns
TableSpecialColumns(identifierType As Integer, table As String, scope As Integer, nullable As Integer) As RowSet
Retrieves the optimal set of columns that uniquely identifies a row in the table and columns that are automatically updated when any value in the row is updated by a transaction. Returns a RowSet.
The identifierType must be either ODBCConstant.SQL_BEST_ROWID or ODBCConstant.SQL_ROWVER, indicating whether to return the optimal list of columns to uniquely identify a row or to return the columns that are automatically updated by a transaction.
scope is the minimum required scope of the row ID, which must be either ODBCConstant.SQL_SCOPE_CURROW, ODBCConstant.SQL_SCOPE_TRANSACTION, or ODBCConstant.SQL_SCOPE_SESSION.
nullable indicates whether to return columns that can have a NULL value, which must be either ODBCConstant.SQL_NO_NULLS or ODBCConstant.SQL_SQL_NULLABLE.
Microsoft provides additional information about the SQLSpecialColumns ODBC function.
ODBCDatabase.Tables
Tables As RowSet
Returns a RowSet with a list of all tables in the database.
A DatabaseException will be raised if an error occurs.
Tables returns a RowSet with one field: TableName As String.
The following code gets and displays the table names for the connected database:
' App.db is a connected database
Var tables As RowSet
tables = App.db.Tables
Try
For Each row As DatabaseRow In tables
MessageBox(row.ColumnAt(0).StringValue)
Next
tables.Close
Catch error As NilObjectException
MessageBox("This database has no tables.")
End Try
Notes
In order to use this class, you must have the ODBCDatabase plug-in in your plugins folder.
The ODBCDatabase class also requires a driver manager and driver. On the Windows platform, the driver manager is supplied by Microsoft as part of Windows or as part of the MDAC package. For non-Windows platforms, the iODBC driver manager is required, which is available from http://www.iodbc.org or is installed with most commercial drivers.
ODBC drivers may be included with the OS, or may be obtained from the database vendor or a commercial developer of ODBC drivers. Non-Windows drivers must be compatible with the iODBC standard. For macOS, Actual Technologies supplies iODBC compliant drivers that work well with Xojo apps. There are other vendors as well.
The driver must match the architecture of the app. So a 64-bit app must use a 64-bit ODBC driver and a 32-bit app must use a 32-bit ODBC driver.
The ODBCDatabase engine supports all four RowSet navigation methods: MoveToFirstRow, MoveToNextRow, MoveToPreviousRow, and MoveToLastRow.
PostgreSQL notes
On macOS, when connecting to PostgreSQL using ODBC you must specify a username and password. If you do not, the ODBC driver will crash your app.
Threading
SelectSQL and ExecuteSQL statements do not block when called from within Threads.
Sample code
This code prompts the user to select a Data Source from either the User or System data sources:
Var db As New ODBCDatabase
db.DataSource = ""
Try
db.Connect
' proceed with database operations
Catch error As DatabaseExcecption
MessageBox("Error: " + error.ErrorMessage)
End Try
This code specifies a specific data source to use:
Var db As New ODBCDatabase
db.DataSource = "TestAccessDB"
Try
db.Connect
' proceed with database operations
Catch error As DatabaseExcecption
MessageBox("Error: " + error.ErrorMessage)
End Try
This code specifies the DSN information to connect to a Microsoft Access database:
Var db As New ODBCDatabase
db.DataSource = "Driver={Microsoft Access Driver (*.mdb)};Dbq=C:\TestAccessDB.mdb;Uid=Admin;Pwd=;"
Try
db.Connect
' proceed with database operations
Catch error As DatabaseExcecption
MessageBox("Error: " + error.ErrorMessage)
End Try
Compatibility
Desktop, Console and Web project types on all supported operating systems.
See also
Database parent class; DatabaseColumn, DatabaseRow, ODBCPreparedStatement, RowSet classes.