TDAESQLCommand
Overview
The TDAESQLCommand class is a base class for all dataset classes in the Data Abstract Architecture.
Please refer to the article How to create a Data Abstract Driver (Delphi) for an overall description.
Location
- Unit: uDAESQLCommand.pas
- Ancestry: TDAEngineBaseObject | TDAESQLCommand
constructor Create virtual
Creates a new instance.
constructor Create(aConnection: IDAConnection; aDataset: TDataset; const aName: string)
Parameters:
- aConnection: Connection
- aDataset: Dataset
- aName: Name
CachedParams protected
property CachedParams: TDictionary<string, Integer> read
CanUseNativeFieldData protected safecall
Specifies that given field can return data in GetNativeFieldData method
function CanUseNativeFieldData(Index: Integer): Boolean
Parameters:
- Index: Required field index
ClearParams protected virtual
Clears parameter values.
procedure ClearParams
Connection protected
Presents the IDAConnection to access information about available databases, tables, columns, etc.
property Connection: IDAConnection read
CreateNativeDatabaseAccess protected virtual
Creates an IDANativeDatabaseAccess implementor.
function CreateNativeDatabaseAccess: IDANativeDatabaseAccess
Dataset
Access to the standard VCL TDataSet.
property Dataset: TDataset read
DoCreateNativeObject protected virtual abstract
Creates a object specific to the given connection.
function DoCreateNativeObject: TObject
DynamicWhere protected
Implementation of Dynamic Where.
property DynamicWhere: TDAWhereBuilder read write
Execute protected virtual safecall abstract
Executes the SQL command.
function Execute: Integer
FindCachedParameter protected
function FindCachedParameter(const AParams: TParams; const AParamName: string): TParam
Parameters:
- AParams:
- AParamName:
FindParameter protected
Finds the AParamName parameter in the |TParams collection.
function FindParameter(const AParams: TParams; const AParamName: string): TParam
Parameters:
- AParams:
- AParamName:
GetDataset protected safecall
Implements IDASQLCommand by returning the result of CreateDataset.
function GetDataset: TDataset
GetName protected safecall
Implements IDASQLCommand by returning a value set in the constructor.
function GetName: string
GetNativeFieldData protected virtual safecall
Sets the DataSize to the according field size value, allocates the Data memory and copies the content of the field.
function GetNativeFieldData(Index: Integer; var Buffer: TBytes): Boolean
Parameters:
- Index: Required field index
- Buffer:
GetNativeFieldDataType protected safecall
Returns the field type of the Index field
function GetNativeFieldDataType(Index: Integer): TFieldType
Parameters:
- Index: field index
GetParams protected safecall
Implements IDASQLCommand by returning the current parameters.
function GetParams: TDAParamCollection
GetParamValues protected virtual safecall abstract
Retrieves the values of the given parameters.
procedure GetParamValues(Params: TDAParamCollection)
Parameters:
- Params: Parameters
GetParamValuesStd protected
Retrieves the values from Params2 for the daptOutput, daptInputOutput and daptResult parameters of Params1.
procedure GetParamValuesStd(Params1: TDAParamCollection; Params2: TParams)
Parameters:
- Params1: Parameters guide
- Params2: Values source
intVCLTypeToDAType protected virtual
Gets mapping |TFieldType to TDADataType.
function intVCLTypeToDAType(aFieldType: TFieldType; ASize: Integer; ADecimalPrecision: Integer; aDecimalScale: Integer): TDADataType
Parameters:
- aFieldType:
- ASize:
- ADecimalPrecision:
- aDecimalScale:
IsTDatasetCompatible protected safecall
Returns true if data access object is TDataset descendant.
function IsTDatasetCompatible: Boolean
Name protected
Returns a human-readable name for the command.
property Name: string read
NativeDatabaseAccess protected
property NativeDatabaseAccess: IDANativeDatabaseAccess read
NativeFieldCount protected safecall
Implements IDASQLCommandNativeObject by
delegating the call to the FNativeDatabaseAccess member.
function NativeFieldCount: Integer
NativeFields protected
property NativeFields[Index: Integer]: IDANativeField read
NativeFindField protected safecall
Implements IDASQLCommandNativeObject by
delegating the call to the FNativeDatabaseAccess member.
function NativeFindField(const FieldName: string): IDANativeField
Parameters:
- FieldName: name of the searched field
NativeObject protected
Access to the standard VCL |TObject which implements the data access.
property NativeObject: TObject read
OnAfterExecute
Fires right after a command was executed.
property OnAfterExecute: TDAAfterExecuteCommandEvent read write
delegate: procedure OnAfterExecute(const Sender: IDASQLCommand; ActualSQL: string; ElapsedMilliseconds: Cardinal)
OnBeforeExecute
Fires before command execution
property OnBeforeExecute: TDABeforeExecuteCommandEvent read write
delegate: procedure OnBeforeExecute(const Sender: IDASQLCommand)
OnExecuteError
Fires when exception is detected during command execution
property OnExecuteError: TDAExecuteCommandErrorEvent read write
delegate: procedure OnExecuteError(const Sender: IDASQLCommand; ActualSQL: string; Error: Exception)
ParamByName protected safecall
Locates a specific parameter, based on its name. If no matching parameter is defined, an exception will be raised.
function ParamByName(const aName: string): TDAParam
Parameters:
- aName: name of the parameter
Params protected
Provides access to the list of parameters defined for the command.
property Params: TDAParamCollection read
Prepared protected
Specifies whether the SQL statement has been prepared for execution on the database (true) or not (false). Setting this property to true will automatically prepare the statement. Preparing statements on the database server allows for faster execution, especially if the statement will be executed multiple times, as the server will not need to re-parse the SQL text for every execution. Please refer to your database system's documentation for more information on preparing statements.
Note that changing the SQL or Where properties will automatically un-prepare the statement.
property Prepared: Boolean read write
PrepareSQLStatement protected virtual abstract
Builds a well formed SQL instruction and prepares it via DoPrepare.
procedure PrepareSQLStatement
RecreateCachedParams protected
procedure RecreateCachedParams(aParams: TParams)
Parameters:
- aParams:
RefreshParams protected virtual safecall
Refreshes the list of parameters defined for the command based on the actual parameter names found in the SQL statement and Where clause.
procedure RefreshParams
SetParamValues protected virtual safecall abstract
Converts values from Data Abstract TDAParam values.
procedure SetParamValues(Params: TDAParamCollection)
Parameters:
- Params: parameters
SetParamValuesStd protected
Utility method to set the values of Params2 (|TParams) for the daptOutput, daptInputOutput and daptResult parameters of Params1 (TDAParamCollection).
procedure SetParamValuesStd(Params1: TDAParamCollection; Params2: TParams)
Parameters:
- Params1: Parameters guide
- Params2: Values holder
SQL protected
Defines the SQL statement to be executed.
property SQL: string read write
SQLContainsDynamicWhere protected virtual safecall
Checks if SQL contains Dynamic Where macros.
function SQLContainsDynamicWhere: Boolean
CachedParams protected
property CachedParams: TDictionary<string, Integer> read
Connection protected
Presents the IDAConnection to access information about available databases, tables, columns, etc.
property Connection: IDAConnection read
Dataset
Access to the standard VCL TDataSet.
property Dataset: TDataset read
DynamicWhere protected
Implementation of Dynamic Where.
property DynamicWhere: TDAWhereBuilder read write
Name protected
Returns a human-readable name for the command.
property Name: string read
NativeDatabaseAccess protected
property NativeDatabaseAccess: IDANativeDatabaseAccess read
NativeFields protected
property NativeFields[Index: Integer]: IDANativeField read
NativeObject protected
Access to the standard VCL |TObject which implements the data access.
property NativeObject: TObject read
Params protected
Provides access to the list of parameters defined for the command.
property Params: TDAParamCollection read
Prepared protected
Specifies whether the SQL statement has been prepared for execution on the database (true) or not (false). Setting this property to true will automatically prepare the statement. Preparing statements on the database server allows for faster execution, especially if the statement will be executed multiple times, as the server will not need to re-parse the SQL text for every execution. Please refer to your database system's documentation for more information on preparing statements.
Note that changing the SQL or Where properties will automatically un-prepare the statement.
property Prepared: Boolean read write
SQL protected
Defines the SQL statement to be executed.
property SQL: string read write
constructor Create virtual
Creates a new instance.
constructor Create(aConnection: IDAConnection; aDataset: TDataset; const aName: string)
Parameters:
- aConnection: Connection
- aDataset: Dataset
- aName: Name
CanUseNativeFieldData protected safecall
Specifies that given field can return data in GetNativeFieldData method
function CanUseNativeFieldData(Index: Integer): Boolean
Parameters:
- Index: Required field index
ClearParams protected virtual
Clears parameter values.
procedure ClearParams
CreateNativeDatabaseAccess protected virtual
Creates an IDANativeDatabaseAccess implementor.
function CreateNativeDatabaseAccess: IDANativeDatabaseAccess
DoCreateNativeObject protected virtual abstract
Creates a object specific to the given connection.
function DoCreateNativeObject: TObject
Execute protected virtual safecall abstract
Executes the SQL command.
function Execute: Integer
FindCachedParameter protected
function FindCachedParameter(const AParams: TParams; const AParamName: string): TParam
Parameters:
- AParams:
- AParamName:
FindParameter protected
Finds the AParamName parameter in the |TParams collection.
function FindParameter(const AParams: TParams; const AParamName: string): TParam
Parameters:
- AParams:
- AParamName:
GetDataset protected safecall
Implements IDASQLCommand by returning the result of CreateDataset.
function GetDataset: TDataset
GetName protected safecall
Implements IDASQLCommand by returning a value set in the constructor.
function GetName: string
GetNativeFieldData protected virtual safecall
Sets the DataSize to the according field size value, allocates the Data memory and copies the content of the field.
function GetNativeFieldData(Index: Integer; var Buffer: TBytes): Boolean
Parameters:
- Index: Required field index
- Buffer:
GetNativeFieldDataType protected safecall
Returns the field type of the Index field
function GetNativeFieldDataType(Index: Integer): TFieldType
Parameters:
- Index: field index
GetParams protected safecall
Implements IDASQLCommand by returning the current parameters.
function GetParams: TDAParamCollection
GetParamValues protected virtual safecall abstract
Retrieves the values of the given parameters.
procedure GetParamValues(Params: TDAParamCollection)
Parameters:
- Params: Parameters
GetParamValuesStd protected
Retrieves the values from Params2 for the daptOutput, daptInputOutput and daptResult parameters of Params1.
procedure GetParamValuesStd(Params1: TDAParamCollection; Params2: TParams)
Parameters:
- Params1: Parameters guide
- Params2: Values source
intVCLTypeToDAType protected virtual
Gets mapping |TFieldType to TDADataType.
function intVCLTypeToDAType(aFieldType: TFieldType; ASize: Integer; ADecimalPrecision: Integer; aDecimalScale: Integer): TDADataType
Parameters:
- aFieldType:
- ASize:
- ADecimalPrecision:
- aDecimalScale:
IsTDatasetCompatible protected safecall
Returns true if data access object is TDataset descendant.
function IsTDatasetCompatible: Boolean
NativeFieldCount protected safecall
Implements IDASQLCommandNativeObject by
delegating the call to the FNativeDatabaseAccess member.
function NativeFieldCount: Integer
NativeFindField protected safecall
Implements IDASQLCommandNativeObject by
delegating the call to the FNativeDatabaseAccess member.
function NativeFindField(const FieldName: string): IDANativeField
Parameters:
- FieldName: name of the searched field
ParamByName protected safecall
Locates a specific parameter, based on its name. If no matching parameter is defined, an exception will be raised.
function ParamByName(const aName: string): TDAParam
Parameters:
- aName: name of the parameter
PrepareSQLStatement protected virtual abstract
Builds a well formed SQL instruction and prepares it via DoPrepare.
procedure PrepareSQLStatement
RecreateCachedParams protected
procedure RecreateCachedParams(aParams: TParams)
Parameters:
- aParams:
RefreshParams protected virtual safecall
Refreshes the list of parameters defined for the command based on the actual parameter names found in the SQL statement and Where clause.
procedure RefreshParams
SetParamValues protected virtual safecall abstract
Converts values from Data Abstract TDAParam values.
procedure SetParamValues(Params: TDAParamCollection)
Parameters:
- Params: parameters
SetParamValuesStd protected
Utility method to set the values of Params2 (|TParams) for the daptOutput, daptInputOutput and daptResult parameters of Params1 (TDAParamCollection).
procedure SetParamValuesStd(Params1: TDAParamCollection; Params2: TParams)
Parameters:
- Params1: Parameters guide
- Params2: Values holder
SQLContainsDynamicWhere protected virtual safecall
Checks if SQL contains Dynamic Where macros.
function SQLContainsDynamicWhere: Boolean
OnAfterExecute
Fires right after a command was executed.
property OnAfterExecute: TDAAfterExecuteCommandEvent read write
delegate: procedure OnAfterExecute(const Sender: IDASQLCommand; ActualSQL: string; ElapsedMilliseconds: Cardinal)
OnBeforeExecute
Fires before command execution
property OnBeforeExecute: TDABeforeExecuteCommandEvent read write
delegate: procedure OnBeforeExecute(const Sender: IDASQLCommand)
OnExecuteError
Fires when exception is detected during command execution
property OnExecuteError: TDAExecuteCommandErrorEvent read write
delegate: procedure OnExecuteError(const Sender: IDASQLCommand; ActualSQL: string; Error: Exception)
- Data Abstract Architecture
- How to create a Data Abstract Driver (Delphi)
- SQL
- Standard VCL ** TObject ** TDataSet ** TFieldType ** TParams ** EDatabaseError