TDataSetSQLStatement c esempio di “class helper” in Delphi.
Gli helper sono un modo per estendere una classe senza utilizzare l’ereditarietà, utile anche per i record che non consentono affatto l’ereditarietà.
La documentazione ufficiale è disponibile all’indirizzo: https://docwiki.embarcadero.com/RADStudio/Sydney/en/Class_and_Record_Helpers_(Delphi).
Spesso mi son trovato a creare del codice per esportare un dataset o un singolo record con i suoi valori in uno statement SQL, e tutte le volte ne ho scritto il codice. Di seguito ho creato un “class helper” per la classe dataset che vi consente di generare gli statement “insert/update/delete”.
Praticamente una volta aggiunta alle vostre unit i TDataSet descendant avranno i metodi “SQLStatement” e “SQLStatements” disponibili per generare il codice SQL desiderato.
Se su un form abbiamo un dataset che si chiama “DSArticoli” e volessimo ottenere il codice di “Insert” per il record corrente basterebbe scrivere:
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FDQuery1.SQLStatement(TSQLStatementType.SQLInsert,'ARTICOLI',[]); |
Di seguito il codice della classe helper per i TDataSet:
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unit uDataSetSSQLHelper; interface uses System.SysUtils, System.Classes, System.IOUtils,DB; type TSQLStatementType = (SQLInsert,SQLUpdate,SQLDelete); TDataSetSQLHelper = class helper for TDataset private function dataTypeSupported(AFieldType : TFieldType) : Boolean; function formatFieldValue(AFld : TField) : String; function whereCondition(KeyFieldNames : TArray<string>; addWhereStmt : Boolean = false):String; function ckKeyFields(KeyFieldNames : TArray<string>) : boolean; function getInsertStatement(TableName: String;KeyFieldNames : TArray<string> = []) : String; function getUpdateStatement(TableName: String;KeyFieldNames : TArray<string> = []) : String; function getDeleteStatement(TableName: String;KeyFieldNames : TArray<string> = []) : String; public function SQLStatement(StatementType: TSQLStatementType; TableName: String;KeyFieldNames : TArray<string> = []) : String; function SQLStatements(StatementType: TSQLStatementType; TableName: String;KeyFieldNames : TArray<string> = []) : String; end; implementation { TDataSetSQLHelper } { TDataSetSQLHelper } function TDataSetSQLHelper.ckKeyFields(KeyFieldNames: TArray<string>): boolean; var LKeyFieldName: string; begin if not Self.Active then raise Exception.Create('Dataset is not active!!'); result := true; for LKeyFieldName in KeyFieldNames do begin if Self.FindField(LKeyFieldName) = nil then begin result := false; raise Exception.Create('KeyFiled "' + LKeyFieldName + '" not found in dataset fields'); end; end; end; function TDataSetSQLHelper.dataTypeSupported(AFieldType: TFieldType): Boolean; begin Result := not(AFieldType in [ ftBlob, ftMemo, ftGraphic, ftFmtMemo, ftParadoxOle, ftDBaseOle, ftTypedBinary, ftCursor, ftFixedChar, ftWideString, ftADT, ftArray, ftReference, ftDataSet, ftOraBlob, ftOraClob, ftVariant, ftInterface, ftIDispatch, ftOraTimeStamp, ftOraInterval, ftConnection, ftParams, ftStream, ftTimeStampOffset, ftObject]); end; function TDataSetSQLHelper.formatFieldValue(AFld: TField): String; var FS : TFormatSettings; begin FS.DecimalSeparator := '.'; FS.CurrencyDecimals := 2; if AFld.IsNull then result := 'null' Else begin case AFld.DataType of ftUnknown: result := '''' + AFld.asString.Replace('''','''''') + ''''; ftString: result := '''' + AFld.asString.Replace('''','''''') + ''''; ftSmallint: result := AFld.asString; ftInteger: result := AFld.asString; ftWord: result := AFld.asString; ftBoolean: result := AFld.AsBoolean.ToString(True); ftFloat: result := FloatToStr(AFld.asFloat); ftCurrency: result := FloatToStr(AFld.asFloat); ftBCD: result := FloatToStr(AFld.asFloat); ftDate: result := '(cast(''' + FormatDateTime('mm/dd/yyyy',AFld.AsDateTime) + ''' as DATE))'; ftTime: result := '(cast(''' + FormatDateTime('hh:mm:ss',AFld.AsDateTime) + ''' as TIME))'; ftDateTime: result := '(cast(''' + FormatDateTime('mm/dd/yyyy hh:mm:ss',AFld.AsDateTime) + ''' as TIMESTAMP))'; ftBytes: AFld.asString; ftVarBytes: AFld.asString; ftAutoInc: AFld.asString; ftLargeint: result := AFld.asString; ftGuid: result := AFld.asString; ftTimeStamp: result := '(cast(''' + FormatDateTime('mm/dd/yyyy hh:mm:ss',AFld.AsDateTime) + ''' as TIMESTAMP))'; ftFMTBcd: FloatToStr(AFld.asFloat); ftFixedWideChar: result := '''' + AFld.asString.Replace('''','''''') + ''''; ftWideMemo: result := '''' + AFld.asString.Replace('''','''''') + ''''; ftLongWord: result := AFld.asString; ftShortint: result := AFld.asString; ftByte: result := AFld.asString; ftExtended: FloatToStr(AFld.asFloat); ftSingle: FloatToStr(AFld.asFloat); end; end; end; function TDataSetSQLHelper.getDeleteStatement(TableName: String; KeyFieldNames: TArray<string>): String; begin ckKeyFields(KeyFieldNames); result := 'delete from ' + TableName + #10#13 + whereCondition(KeyFieldNames,true); end; function TDataSetSQLHelper.getInsertStatement(TableName: String; KeyFieldNames: TArray<string>): String; var I: Integer; LFieldList: String; LValueList: String; begin LFieldList := ''; LValueList := ''; ckKeyFields(KeyFieldNames); result := 'insert into ' + TableName + '(' + #10#13; for I := 0 to Self.FieldCount-1 do begin if dataTypeSupported(Self.Fields[I].DataType) then begin if LFieldList = '' then LFieldList := Self.Fields[I].FieldName else LFieldList := LFieldList + ',' + Self.Fields[I].FieldName; end; end; result := result + LFieldList + ')values(' + #10#13; for I := 0 to Self.FieldCount-1 do begin if dataTypeSupported(Self.Fields[I].DataType) then begin if LValueList = '' then LValueList := formatFieldValue(Self.Fields[I]) else LValueList := LValueList + ',' + formatFieldValue(Self.Fields[I]); end; end; result := result + LValueList + ')'; end; function TDataSetSQLHelper.getUpdateStatement(TableName: String; KeyFieldNames: TArray<string>): String; var I: Integer; begin ckKeyFields(KeyFieldNames); Result := 'update ' + TableName + ' set '; for I := 0 to Self.FieldCount-1 do begin if dataTypeSupported(Self.Fields[I].DataType) then begin Result := Result + #1013 + Self.Fields[I].Name + ' = ' + formatFieldValue(Self.Fields[I]); if I < Self.FieldCount-1 then Result := Result + ' ,'; end; end; Result := Result + #10#13 + whereCondition(KeyFieldNames); end; function TDataSetSQLHelper.SQLStatement(StatementType: TSQLStatementType; TableName: String; KeyFieldNames: TArray<string>): String; begin case StatementType of SQLInsert: result := getInsertStatement(TableName,KeyFieldNames); SQLUpdate: result := getUpdateStatement(TableName,KeyFieldNames); SQLDelete: result := getDeleteStatement(TableName,KeyFieldNames); end; end; function TDataSetSQLHelper.SQLStatements(StatementType: TSQLStatementType; TableName: String; KeyFieldNames: TArray<string>): String; begin Result := ''; Self.First; while not Self.Eof do begin if Result = '' then Result := SQLStatement(StatementType,TableName,KeyFieldNames) + ';' Else Result := Result + #10#13 + SQLStatement(StatementType,TableName,KeyFieldNames) + ';'; Self.Next; end; end; function TDataSetSQLHelper.whereCondition( KeyFieldNames: TArray<string>; addWhereStmt : Boolean = false): String; var I: Integer; LFieldName: string; function addCondition(KeyFieldName : String) : String; begin result := '(' + KeyFieldName + ' = ' + formatFieldValue(Self.FieldByName(KeyFieldName)) + ')'; end; begin result := ''; if (KeyFieldNames = nil)or(Length(KeyFieldNames) = 0) then begin for I := 0 to Self.FieldCount-1 do begin if dataTypeSupported(Self.Fields[I].DataType) then begin LFieldName := Self.Fields[I].FieldName; if result = '' then result := addCondition(LFieldName) + #10#13 else result := result + 'and' + addCondition(LFieldName) + #10#13; end end end else begin for LFieldName in KeyFieldNames do begin if result = '' then result := addCondition(LFieldName) + #10#13 else result := result + 'and' + addCondition(LFieldName) + #10#13; end end; if addWhereStmt then result := ' where (' + result + ')'; end; end. |
