DB unit

Database access layer.

The db unit provides the basis for all database access mechanisms. It introduces abstract classes, on which all database access mechanisms are based: TDataset representing a set of records from a database, TField which represents the contents of a field in a record, TDatasource which acts as an event distributor on behalf of a dataset and TParams which can be used to parameterize queries. The databases connections themselves are abstracted in the TDatabase class.

Classes and records

`EDatabaseError`	class	Base class for all database-related errors.
`EUpdateError`	class	Error raised when updating data during a post operation.
`IProviderSupport`	interface	Interface for Provider support.
`TArrayField`	class
`TAutoIncField`	class	Field for auto-incremental, 32-bit signed integer data.
`TBCDField`	class	Field class for Binary Coded Decimal (BCD) values.
`TBinaryField`	class	Field class for working with binary field data.
`TBlobField`	class	Base class for BLOB field data.
`TBooleanField`	class	Boolean field class type.
`TByteField`	class	Field class for 8-bit unsigned integer data.
`TBytesField`	class	Field class for fixed size byte array values.
`TCheckConstraint`	class	Record-level constraint definition.
`TCheckConstraints`	class	Set of record-level constraints.
`TCurrencyField`	class	Class for currency fields.
`TCustomConnection`	class	Abstract class for connections to a server.
`TDatabase`	class	Base class for connecting a FreePascal application to an external Database engine.
`TDataLink`	class	Data event handling agent for controls.
`TDataSet`	class	Base class for records-based data-access.
`TDataSetEnumerator`	class	Enumerator for TDataset records.
`TDataSource`	class	Component representing the link between a local (GUI) component and a dataset.
`TDateField`	class	Field class for date values.
`TDateTimeField`	class	Field class for date/time/Datetime values.
`TDateTimeRec`	record	Date/Time record.
`TDBDataset`	class	Dataset connected to a database.
`TDBTransaction`	class	Encapsulate a transaction.
`TDefCollection`	class	Definition collection.
`TDetailDataLink`	class	Represents the link between a detail data source and a master datasource.
`TExtendedField`	class
`TField`	class	Provide access to the contents of a single field in a record.
`TFieldDef`	class	Class to describe one field in a record in a dataset.
`TFieldDefs`	class	Collection of TFieldDef instances.
`TFields`	class	Collection of instances.
`TFieldsEnumerator`	class	Default enumerator for the fields collection of a dataset.
`TFloatField`	class	Class for floating point values.
`TFMTBCDField`	class	Fixed precision floating point data field.
`TGraphicField`	class	Field class for graphical BLOB field data.
`TGuidField`	class	Field class for native variant data.
`TIndexDef`	class	Index definition.
`TIndexDefs`	class	A class to keep a list of index definitions.
`TIntegerField`	class	Alias for TLongintField.
`TLargeintField`	class	Field class for 64-bit signed integer data.
`TLongintField`	class	Field class for 32-bit signed integer data.
`TLongWordField`	class	Field class for 32-bit unsigned integer data.
`TLookupList`	class	Class to manage lookup list values.
`TLookupListRec`	record	Record to store lookup results.
`TMasterDataLink`	class	Datalink for Master-Detail relationships between datasets.
`TMasterParamsDataLink`	class	Class to establish a master-detail relationship between dataset, based on parameters.
`TMemoField`	class	Base class for MEMO (text BLOB) field data.
`TNamedItem`	class	Named collection item.
`TNumericField`	class	Base class for all numerical data field classes.
`TObjectField`	class
`TParam`	class	Parameter description class.
`TParams`	class	A collection of parameter values for SQL-based datasets.
`TParamsEnumerator`	class	Enumerator for parameters.
`TShortintField`	class	Field class for 8-bit signed integer data.
`TSingleField`	class
`TSmallintField`	class	Field class for smallint (16-bit signed integer) data.
`TStringField`	class	Field class to handle ansistring fields.
`TTimeField`	class	Field class for time values.
`TVarBytesField`	class	Field class for variable size byte array values.
`TVariantField`	class	Field class for native variant data.
`TWideMemoField`	class	Field class for wide MEMO (widestring text BLOB) field data.
`TWideStringField`	class	Field class for widestring data.
`TWordField`	class	Field class for word (16-bit unsigned integer) data.

Procedures and functions

`BuffersEqual`	function	Check whether 2 memory buffers are equal.
`DatabaseError`	procedure	Raise an EDatabaseError exception.
`DatabaseErrorFmt`	procedure	Raise an EDatabaseError exception with a formatted message.
`DateTimeRecToDateTime`	function	Convert TDateTimeRec record to a TDateTime value.
`DateTimeToDateTimeRec`	function	Convert TDateTime value to a TDateTimeRec record.
`DisposeMem`	procedure	Dispose of a heap memory block and Nil the pointer (deprecated).
`enumerator(TDataSet):TDataSetEnumerator`	operator	Operator to return dataset enumerator.
`ExtractFieldName`	function	Extract the field name at position.
`SkipComments`	function	Skip SQL comments.

Types

`LargeInt`	type	Large (64-bit) integer.
`PBookmarkFlag`	type	Pointer to TBookmarkflag type.
`PBufferList`	type	Pointer to TBufferlist type.
`PDateTimeRec`	type	Pointer to TDateTimeRec record.
`PLargeInt`	type	Pointer to Large (64-bit) integer.
`PLookupListRec`	type	Pointer to TLookupListRec record.
`TBlobData`	type	Alias type to store blob data.
`TBlobStreamMode`	enumeration	Mode used when creating a blob stream.
`TBlobType`	type	Valid BLOB fieldtypes.
`TBookMark`	type	Bookmark type.
`TBookmarkFlag`	enumeration	Bookmark flags.
`TBookmarkStr`	type	Bookmark as string type - deprecated.
`TBufferArray`	type	Pointer to an array of buffers.
`TBufferList`	type	Array of PChar records.
`TCloseErrorEvent`	procedure type
`TDataAction`	enumeration	Action to take when a data manipulation operation has failed.
`TDatabaseClass`	type	Class pointer for TDatabase.
`TDataChangeEvent`	procedure type	Event handler prototype when a field's data has changed.
`TDataEvent`	enumeration	Various events that are sent to datasources.
`TDataOperation`	procedure type	Internal callback type.
`TDatasetClass`	type	Class type for the TDataset class.
`TDataSetErrorEvent`	procedure type	Error handling callback.
`TDataSetNotifyEvent`	procedure type	Event handler prototype for dataset events.
`TDataSetState`	enumeration	Current state of the dataset.
`TDateTimeAlias`	type	Alias for TDateTime type.
`TDBDatasetClass`	type	Class of TDBDataset.
`TFieldAttribute`	enumeration	Field attributes.
`TFieldAttributes`	set	Set of TFieldAttribute values.
`TFieldChars`	set	Set of valid characters for the field contents.
`TFieldClass`	type
`TFieldDefClass`	type	Class of TFieldDef.
`TFieldDefsClass`	type	Class of TFieldDefs.
`TFieldGetTextEvent`	procedure type	Event handler to get field content.
`TFieldKind`	enumeration	Kind of field.
`TFieldKinds`	set	Set of TFieldKind values.
`TFieldMap`	type	Array type with TFieldType as index type.
`TFieldNotifyEvent`	procedure type	Notification handler prototype.
`TFieldRef`	type	Pointer to a TField instance.
`TFieldsClass`	type	Class of TFields.
`TFieldSetTextEvent`	procedure type	Event handler to get field content.
`TFieldType`	enumeration	Field data type description.
`TFilterOption`	enumeration	Available filter options.
`TFilterOptions`	set	Set of filter options to use.
`TFilterRecordEvent`	procedure type	Record filtering event handler prototype.
`TGetMode`	enumeration	Get new buffer mode.
`TGetResult`	enumeration	result of the GetRecord operation.
`TIndexOption`	enumeration	Index description flags.
`TIndexOptions`	set	Set of TIndexOption values.
`TLocateOption`	enumeration	Available options when locating a record in a dataset.
`TLocateOptions`	set	Options to use when locating a record in a dataset.
`TLoginEvent`	procedure type	Login event handler.
`TParamBinding`	type	Auxiliary type, used when binding parameters.
`TParamClass`	type	Class of TParam.
`TParamStyle`	enumeration	Style of parameter.
`TParamType`	enumeration	Parameter type.
`TParamTypes`	set	Set of TParamType.
`TProviderFlag`	enumeration	What to do with fields when applying updates.
`TProviderFlags`	set	Set of flags.
`TPSCommandType`	enumeration	Type of SQL command.
`TRecordBuffer`	type	Pointer type for record data buffer.
`TRecordBufferBaseType`	type	Opaque base type for TRecordBuffer.
`TResolverResponse`	enumeration	Resolver response code.
`TResyncMode`	set	Internal flag for resynchronisation.
`TSQLParseOption`	enumeration	Represents SQL parser options available to the TParams collection.
`TSQLParseOptions`	set	Set type used to store value(s) from the TSQLParseOption enumeration.
`TStringFieldBuffer`	type	Type to access string field content buffers as an array of characters.
`TUpdateAction`	enumeration	Action to perform when an update operation fails.
`TUpdateKind`	enumeration	Kind of update operation.
`TUpdateMode`	enumeration	Update mode.
`TUpdateStatus`	enumeration	Record update status.
`TUpdateStatusSet`	set	Set of update states.

Constants

`DefaultFieldClasses`	constant	Default field classes to use when creating a new TField instance.
`dsEditModes`	constant	Edit modes.
`dsMaxBufferCount`	constant	Maximum data buffers count for dataset.
`dsMaxStringSize`	constant	Maximum size of string fields.
`dsWriteModes`	constant	Field write modes.
`FieldTypeNames`	constant	Human-readable names of field types.
`FieldTypetoVariantMap`	constant	Map field types on variant types.
`ftBlobTypes`	constant	Constant enumerating all blob types.
`ObjectFieldTypes`	constant
`SQLDelimiterCharacters`	constant	SQL statement delimiter token characters.
`YesNoChars`	constant	Array of characters mapping a boolean to Y/N.

Variables

LoginDialogExProc variable Login dialog callback.

Uses

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.