用DAO方式建立Access數據庫的方法的疑問 |
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尚未結案
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alex_soong
一般會員   發表：2 回覆：3 積分：1 註冊：2004-11-04 發送簡訊給我 |
我有一個很簡單的項目，使用了Access數據庫，打算在程式啓動時檢測是否有數据庫，並建立數據庫。結果卻引來了一堆問題。
1.建立一個Access數據庫
const
accessstring = 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%s'; procedure CreateDatabase(DBName: string);
var
DB: OleVariant;
tempstr: string;
begin
DB := CreateOleObject('ADOX.Catalog');
try
tempstr := format(accessstring,[DBName]);
DB.Create(tempstr);
finally
DB:=Unassigned;
end;
end; 黨建立好數據庫之後，該如何再次打開這個數據庫並添加表呢？？ 2.黨要建立一個新表時，縂要先查詢一次是否有同名的表單，但爲什麽總是連系統表單一起返回了，怎麽辦？
type
TAccessTableDef = record
Name,
DateCreated,
LastUpdated,
Description: string;
end;
pTaccessTableDef = ^TAccessTableDef; procedure GetTableDefs(const DBName: string; TableDefsList: Tlist);
var
DBEngine, DB: OleVariant;
I: Longint;
temppointer: pTaccessTableDef;
begin
try
DBEngine := CreateOleObject('DAO.DBEngine.36');
DB := DBEngine.OpenDatabase(DBName);
if Longint(DB.TableDefs.Count) > 0 then
begin
for I := 0 to Longint(DB.TableDefs.Count)-1 do
begin
new(temppointer);
temppointer.Name := DB.TableDefs[I].Name;
temppointer.DateCreated := DB.TableDefs[I].DateCreated;
temppointer.LastUpdated := DB.TableDefs[I].LastUpdated;
try
temppointer.Description := DB.TableDefs[I].Properties['Description'].Value;
except
temppointer.Description := '';
end;
TableDefsList.Add(temppointer);
end; //for I := 0 to Longint(DB.TableDefs.Count)-1 do
end; // if Longint(DB.TableDefs.Count) > 0 then
finally
DB := Unassigned;
DBEngine := Unassigned;
end;
end; 3.請教各位，何處能找到用DAO的方法建立Access數據庫的文檔資料，謝謝
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alex_soong
一般會員 發表：2 回覆：3 積分：1 註冊：2004-11-04 發送簡訊給我 |
鬱悶了好久，終于搞定了。哈哈
獻上整個函數單元供大家參考； unit DatabaseUnit; interface
uses Windows, Messages, SysUtils, Variants, Classes,comobj,DB,ADODB,Controls; procedure CreateDatabase(DBName: string); //建立Access数据库
Procedure _CreateDatabaseTable(DBName: string; Tablenames:Tstrings; FieldDefsListArray: array of Tlist; arraycount: integer); //建立Access数据库中的表
procedure GetTableDefs(const DBName: string; TableDefsList: Tlist); //获得Access数据库中的表信息
procedure GetFieldDefs(const DBName, TableName: string; FieldDefsList: Tlist); //获得Access数据库中的每个表中的字段信息
procedure RenameField(const TableName, OldColName, NewColName: string; ADOConnection:TADOConnection ); //动态修改Access数据库字段内容
function CheckTablename(Const DBName, TableName: string): boolean;
implementation uses VariableUnit; procedure CreateDatabase(DBName: string); //建立access数据库
var
DB: OleVariant;
tempstr: string;
begin
DB := CreateOleObject('ADOX.Catalog');
try
tempstr := format(accessstring,[DBName]);
DB.Create(tempstr);
finally
DB:=Unassigned;
end;
end; Procedure _CreateDatabaseTable(DBName: string; Tablenames:Tstrings; FieldDefsListArray: array of Tlist; arraycount: integer); //建立Access数据库中的表
var
DB,tables,Cols: OleVariant; //DBEngine,
temploop1,temploop2: integer;
temppointer: pTAccessFieldDef;
tempADOConnection:TADOConnection;
tempstr: string;
begin
if not FileExists(DBName) then //如果没有发现数据库就建立数据库
CreateDatabase(DBName);
if TableNames.Count <= 0 then exit;
if TableNames.Count <> arraycount then exit; //名称和字段信息个数不一致，就退出 // DBEngine := CreateOleObject('DAO.DBEngine.36');
//DB := DBEngine.OpenDatabase(DBName); DB := CreateOleObject('ADOX.Catalog');
tempADOConnection := TADOConnection.Create(nil);
tempstr := format(accessstring,[DBName]);
tempADOConnection.ConnectionString := tempstr;
tempADOConnection.Open;
DB.ActiveConnection := tempADOConnection.ConnectionObject; try
for temploop1 := 0 to TableNames.Count -1 do
begin
if CheckTablename(DBName,TableNames[temploop1]) then //如果没有同名就建立
begin
tables := CreateOleObject('ADOX.Table'); tables.ParentCatalog := DB;
tables.name := TableNames[temploop1]; //表建立好之后，就开始建立字段
if FieldDefsListArray[temploop1].Count > 0 then
begin
for temploop2 := 0 to FieldDefsListArray[temploop1].Count -1 do
begin
temppointer := FieldDefsListArray[temploop1].Items[temploop2];
Cols := CreateOleObject('ADOX.Column');
Cols.ParentCatalog := DB;
case temppointer.Types of
adInteger: begin
Cols.Name := temppointer.Name;
Cols.type := temppointer.Types;
Cols.DefinedSize := temppointer.Size;
Cols.Properties['Autoincrement'].Value := strtobool(temppointer.Autoincrement);
Cols.Properties['Description'].Value := temppointer.Description;
tables.Columns.Append(Cols, adEmpty, 0);
Cols := Unassigned;
end;
adVarWChar: begin
Cols.Name := temppointer.Name;
Cols.type := temppointer.Types;
Cols.DefinedSize := temppointer.Size;
Cols.Properties['Description'].Value := temppointer.Description;
tables.Columns.Append(Cols, adEmpty, 0);
Cols := Unassigned;
end;
adLongVarWChar: begin
Cols.Name := temppointer.Name;
Cols.type := temppointer.Types;
Cols.DefinedSize := temppointer.Size;
Cols.Properties['Description'].Value := temppointer.Description;
tables.Columns.Append(Cols, adEmpty, 0);
Cols := Unassigned;
end;
end; //case temppointer.Types of end; //for temploop2 := 0 to FieldDefsListArray[temploop1].Count -1 do DB.Tables.Append(tables);
tables:= Unassigned; //每个表的所有字段都建立好之后，就注销，进入下一个表
Cols:= Unassigned;
end
else //if FieldDefsListArray[temploop1].Count > 0 then 如果字段小于等于0 就不要建立这个表的字段，
begin //进入下一张表
tables:= Unassigned;
Cols:= Unassigned;
end; end //if CheckTablename(DBName,TableNames[temploop1]) then //如果没有同名就建立
end; //for temploop1 := 0 to TableNames.Count -1 do
finally
//DBEngine:= Unassigned;
tempADOConnection.Close;
DB:= Unassigned;
tables:= Unassigned;
Cols:= Unassigned;
tempADOConnection.Free;
end; end; procedure GetTableDefs(const DBName: string; TableDefsList: Tlist); //获得Access数据库中的表信息
var
DBEngine, DB: OleVariant;
I: Longint;
temppointer: pTaccessTableDef;
begin
try
DBEngine := CreateOleObject('DAO.DBEngine.36');
DB := DBEngine.OpenDatabase(DBName);
if Longint(DB.TableDefs.Count) > 0 then
begin
for I := 0 to Longint(DB.TableDefs.Count)-1 do
begin
new(temppointer);
temppointer.Name := DB.TableDefs[I].Name;
temppointer.DateCreated := DB.TableDefs[I].DateCreated;
temppointer.LastUpdated := DB.TableDefs[I].LastUpdated;
try
temppointer.Description := DB.TableDefs[I].Properties['Description'].Value;
except
temppointer.Description := '';
end;
TableDefsList.Add(temppointer);
end; //for I := 0 to Longint(DB.TableDefs.Count)-1 do
end; // if Longint(DB.TableDefs.Count) > 0 then
finally
DB := Unassigned;
DBEngine := Unassigned;
end;
end; procedure GetFieldDefs(const DBName, TableName: string; FieldDefsList: Tlist); //获得Access数据库中的每个表中的字段信息
var
DBEngine, DB: OleVariant;
I: Longint;
temppointer: pTAccessFieldDef;
begin
try
DBEngine := CreateOleObject('DAO.DBEngine.36');
DB := DBEngine.OpenDatabase(DBName);
if Longint(DB.TableDefs[TableName].Fields.Count) > 0 then
begin
for I := 0 to Longint(DB.TableDefs[TableName].Fields.Count) -1 do
begin
new(temppointer);
temppointer.Name := DB.TableDefs[TableName].Fields[I].Name;
temppointer.Types := DB.TableDefs[TableName].Fields[I].Type;
temppointer.Size := DB.TableDefs[TableName].Fields[I].Size;
try
temppointer.Description := DB.TableDefs[TableName].Fields[I].Properties['Description'].Value;
except
temppointer.Description := '';
end;
FieldDefsList.Add(temppointer);
end; //Longint(DB.TableDefs[TableName].Fields.Count) > 0
end; // Longint(DB.TableDefs[TableName].Fields.Count) > 0
finally
DB := Unassigned;
DBEngine := Unassigned;
end;
end; //TableName: 表名; OldColName: 原字段名; NewColName: 新字段名;
procedure RenameField(const TableName, OldColName, NewColName: string; ADOConnection:TADOConnection );
var
DB, Col: OleVariant;
begin
try
DB := CreateOleObject('ADOX.Catalog');
DB.ActiveConnection := ADOConnection.ConnectionObject;
Col := CreateOleObject('ADOX.Column');
Col := DB.Tables[TableName].Columns[OldColName];
Col.Name := NewColName;
finally
DB := Unassigned;
Col := Unassigned;
end;
end; function CheckTablename(Const DBName, TableName: string): boolean; //true 表示没有检测到相同表名，就可以建立，
var //false 表示检测到相同表名，不可以建立
tableNamelist: Tlist;
temploop: integer;
temppointer: pTaccessTableDef;
begin
result := false;
if not FileExists(DBName) then
CreateDatabase(DBName); tableNamelist := Tlist.Create;
try
GetTableDefs(DBName,tableNameList);
if tableNamelist.Count > 0 then
begin
for temploop := 0 to TableNameList.Count -1 do
begin
temppointer := TableNamelist.Items[temploop];
if UpperCase(tableName) = UpperCase(temppointer.Name) then
exit;
end;
end;
result := true; //如果里面没有表也可以返回true
finally
tableNamelist.Clear;
tablenamelist.Free;
end;
end; end.
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發表時間：2005-06-07 11:36:46
IP:218.2.xxx.xxx 未訂閱
系統時間：2024-06-29 14:37:43
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