Okay so basically I've been working on my computing project for a while now and I've got 90% of it working however I'm having a problem with Delphi where is says that my database is not connected/ there is a problem connecting however I've already tried writing the information to the screen and this showed me that the items I was looking to pick up where in fact being picked up so the failure is when the items are being input in to the database. This however shouldn't be happening as the System already has database information displayed from that table and the user can physically select things from the database tables within the program however when trying to store the information back into the database it just breaks. Me and my computing teacher can not work it out, any help would be appreciated.
The problem appears on the new orders page. If you'd rather look at the system then you can download it from here https://drive.google.com/folderview?id=0B_iRfwwM9QpHVXJnSkx4U1FjMlk&usp=sharing
procedure Tform1.btnSaveClick(Sender: TObject);
var orderID:integer;
count:integer;
begin
try
//save into the order table first
tblOrder.Open;
tblOrder.Insert;
tblOrder.FieldByName('CustomerID').value:= strtoint(cboCustomer.Text);
tblOrder.Close;
tblOrder.Open;
tblOrder.Last;
orderID:=tblOrder.FieldByName('OrderID').Value;
showmessage(inttostr(orderID));
for count := 1 to nextFree-1 do
begin
if itemOrdered[count,1]<>0 then
begin
tblOrderLine.Open;
tblOrderLine.AppendRecord([orderID, itemOrdered[count,1],itemOrdered[count,2]]);
end;
end;
showmessage('The order has been saved');
except
showmessage('There was a problem connecting to the database');
end;
end;
You're doing far too much open, do something, close, open. Don't do that, because it's almost certain that is the cause of your problem. If the data is already being displayed, the database is open already. If you want it to keep being displayed, the database has to remain open.
I also removed your try..except. You can put it back in if you'd like; I personally like to allow the exception to occur so that I can find out why the database operation failed from the exception message, rather than hide it and have no clue what caused it not to work.
procedure Tform1.btnSaveClick(Sender: TObject);
var
orderID: integer;
count: integer;
begin
//save into the order table first
tblOrder.Insert;
tblOrder.FieldByName('CustomerID').value:= strtoint(cboCustomer.Text);
tblOrder.Post;
orderID:=tblOrder.FieldByName('OrderID').Value;
showmessage(inttostr(orderID));
for count := 1 to nextFree-1 do
begin
if itemOrdered[count, 1] <> 0 then
begin
tblOrderLine.AppendRecord([orderID, itemOrdered[count,1],itemOrdered[count,2]]);
tblOrderLine.Post;
end;
end;
showmessage('The order has been saved');
end;
Related
I have a db function that populates data from active directory into a table in the database. It works fine without giving any errors.
Next step is to schedule a job in db so that it is run everyday automatically. When I do that, I get this error: ORA-01008: not all variables are mapped
The code I am using in the PL/SQL block is this:
DECLARE
v_Return VARCHAR2(200);
BEGIN
v_Return := PRE_JOB_FUNCTION();
:v_Return := v_Return;
END;
I think that the issue is that v_Return needs to be Null to begin the execution of this function but I am confused how to do that. Can someone please help?
I'm stumped on something which should be very straight-forward. I have a SQL Server database, and I'm trying to update a non-nullable varchar or nvarchar field with an empty string. I know it's possible, because an empty string '' is not the same thing as NULL. However, using the TADOQuery, it is not allowing me to do this.
I'm trying to update an existing record like so:
ADOQuery1.Edit;
ADOQuery1['NonNullFieldName']:= '';
//or
ADOQuery1.FieldByName('NonNullFieldName').AsString:= '';
ADOQuery1.Post; //<-- Exception raised while posting
If there is anything in the string, even just a single space, it saves just fine, as expected. But, if it is an empty string, it fails:
Non-nullable column cannot be updated to Null.
But it's not null. It's an empty string, which should work just fine. I swear I've passed empty strings many, many times in the past.
Why am I getting this error, and what should I do to resolve it?
Additional details:
Database: Microsoft SQL Server 2014 Express
Language: Delphi 10 Seattle Update 1
Database drivers: SQLOLEDB.1
Field being updated: nvarchar(MAX) NOT NULL
I can reproduce your reported problem using the code below with SS2014, the OLEDB driver and
Seattle and the difference in behaviour when the table has been created with MAX as the column size and a specific number (4096 in my case). I thought I would post this is as an alternative
answer because it not only shows how to investigate this difference systematically
but also identifies why this difference arises (and hence how to avoid it in future).
Please refer to and execute the code below, as written, i.e. with the UseMAX define
active.
Turning on "Use Debug DCUs" in the the project options before executing the code, immediately
reveals that the described exception occurs in Data.Win.ADODB at line 4920
Recordset.Fields[TField(FModifiedFields[I]).FieldNo-1].Value := Data
of TCustomADODataSet.InternalPost and the Debug evaluation window reveals that
Data at this point is Null.
Next, notice that
update jdtest set NonNullFieldName = ''
executes in an SSMS2014 Query window without complaint (Command(s) completed successfully.), so it seems that the
fact that Data is Null at line 4920 is what is causing the problem and the next question is "Why?"
Well, the first thing to notice is that the form's caption is displaying ftMemo
Next, comment out the UseMAX define, recompile and execute. Result: No exception
snd notice that the form's caption is now displaying ftString.
And that's the reason: Using a specific number for the column size means that
the table metadata retrieved by the RTL causes the client-side Field to be created
as a TStringField, whose value you can set by a string assignment statement.
OTOH, when you specify MAX, the resulting client-side Field is of type ftMemo,
which is one of Delphi's BLOB types and when you assign
string values to an ftMemo field, you are at the mercy of code in Data.DB.Pas , which does all the reading (and writing) to the record buffer using a TBlobStream. The problem with that is that as far as I can see, after a lot of experiments and tracing through the code, the way a TMemoField uses a BlobStream fails to properly distinguish between updating the field contents to '' and setting the field's value to Null (as in System.Variants).
In short, whenever you try to set a TMemoField's value to an empty string, what actually happens is that the field's state is set to Null, and this is what causes the exception in the q. AFAICS, this is unavoidable, so no work-around is obvious, to me at any rate.
I have not investigated whether the choice between ftMemo and ftString is made by the Delphi RTL code or the MDAC(Ado) layer it sits upon: I would expect it is actually determined by the RecordSet TAdoQuery uses.
QED. Notice that this systematic approach to debugging has revealed the
problem & cause with very little effort and zero trial and error, which was
what I was trying to suggest in my comments on the q.
Another point is that this problem could be tracked down entirely without
resorting to server-side tools including the SMSS profiler. There wasn't any need to use the profiler to inspect what the client was sending to the server
because there was no reason to suppose that the error returned by the server
was incorrect. That confirms what I said about starting investigation at the client side.
Also, using a table created on the fly using IfDefed Sql enabled the problem effectively to be isolated in a single step by simple observation of two runs of the app.
Code
uses [...] TypInfo;
[...]
implementation[...]
const
// The following consts are to create the table and insert a single row
//
// The difference between them is that scSqlSetUp1 specifies
// the size of the NonNullFieldName to 'MAX' whereas scSqlSetUp2 specifies a size of 4096
scSqlSetUp1 =
'CREATE TABLE [dbo].[JDTest]('#13#10
+ ' [ID] [int] NOT NULL primary key,'#13#10
+ ' [NonNullFieldName] VarChar(MAX) NOT NULL'#13#10
+ ') ON [PRIMARY]'#13#10
+ ';'#13#10
+ 'Insert JDTest (ID, [NonNullFieldName]) values (1, ''a'')'#13#10
+ ';'#13#10
+ 'SET ANSI_PADDING OFF'#13#10
+ ';';
scSqlSetUp2 =
'CREATE TABLE [dbo].[JDTest]('#13#10
+ ' [ID] [int] NOT NULL primary key,'#13#10
+ ' [NonNullFieldName] VarChar(4096) NOT NULL'#13#10
+ ') ON [PRIMARY]'#13#10
+ ';'#13#10
+ 'Insert JDTest (ID, [NonNullFieldName]) values (1, ''a'')'#13#10
+ ';'#13#10
+ 'SET ANSI_PADDING OFF'#13#10
+ ';';
scSqlDropTable = 'drop table [dbo].[jdtest]';
procedure TForm1.Test1;
var
AField : TField;
S : String;
begin
// Following creates the table. The define determines the size of the NonNullFieldName
{$define UseMAX}
{$ifdef UseMAX}
S := scSqlSetUp1;
{$else}
S := scSqlSetUp2;
{$endif}
ADOConnection1.Execute(S);
try
ADOQuery1.Open;
try
ADOQuery1.Edit;
// Get explicit reference to the NonNullFieldName
// field to make working with it and investigating it easier
AField := ADOQuery1.FieldByName('NonNullFieldName');
// The following, which requires the `TypInfo` unit in the `USES` list is to find out which exact type
// AField is. Answer: ftMemo, or ftString, depending on UseMAX.
// Of course, we could get this info by inspection in the IDE
// by creating persistent fields
S := GetEnumName(TypeInfo(TFieldType), Ord(AField.DataType));
Caption := S; // Displays `ftMemo` or `ftString`, of course
AField.AsString:= '';
ADOQuery1.Post; //<-- Exception raised while posting
finally
ADOQuery1.Close;
end;
finally
// Tidy up
ADOConnection1.Execute(scSqlDropTable);
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
Test1;
end;
The problem occurs when using MAX in the data type. Both varchar(MAX) and nvarchar(MAX) exploit this behavior. When removing MAX and replacing it with a large number, such as 5000, then it allows empty strings.
In my form, i have a TDBGRid, TDatasource , MessageTable and 2 button. I have a button to add new row in my DBGRID :
MessageTable.Append;
MessageTable.Edit;
MessageTable.FieldByName('FieldName').AsString := sName;
MessageTable.Post;
The second button is used to delete a current row :
MessageTable.Edit ;
MessageTable.Delete ;
How can ensure all Cell not empty before the post?
If there is an empty Cell, i need to ignore this row !
how can I do that?
You should use the features the dataset (in this case, TTable) already give you instead of trying to reinvent the wheel. TDataSet provides an event (OnBeforePost) that is specifically designed for this purpose.
Click on your TTable, and then switch to the Events tab in the Object Inspector. Find the OnBeforePost event and double click it to generate the event shell in the Code Editor. You'll see something like this:
procedure TForm1.Table1BeforePost(DataSet: TDataSet);
begin
// DataSet is the TDataSet (TTable, TQuery, TADOQuery, etc.) to which
// event is attached
end;
You can do all of your validations needed before a record is actually written to the database here. For instance, if you want to make sure every single field has something in it, you can do this:
procedure TForm1.Table1BeforePost(DataSet: TDataSet);
var
i: Integer;
begin
// You can replace DataSet with your actual table variable name, but using it
// this way allows you to use this same event for more than one table if you want.
for i := 0 to DataSet.FieldCount - 1 do
if DataSet.Fields[i].IsNull then
raise Exception.CreateFmt('Field %s has no value', DataSet.Fields[i].FieldName);
end;
If you want to make sure only certain fields have values, or that the value is within a certain range, you can access the field directly:
procedure TForm1.Table1BeforePost(DataSet: TDataSet);
begin
if DataSet.FieldByName('MyField').IsNull then
Abort; // This silently cancels the post without telling the user
if DataSet.FieldByName('AField').AsInteger = 0 then
raise Exception.Create('AField must not be 0');
end;
Now you don't have to do anything at all in your TDBGrid. If the user hits DownArrow on the last row and a new row is inserted, and they enter incomplete or wrong data, the events above will take care of it. They'll also work if you use two buttons (one to insert or edit and the other to post), because the events will handle everything else.
procedure TForm1.ButtonInsertClick(Sender: TObject);
begin
Table1.Insert; // Or Append - if you have an index on the table they're the same thing
end;
procedure TForm1.ButtonPostClick(Sender: TObject);
begin
Table1.Post; // This is 100% of the code you need here
end;
Hi, everybody.
I am new to PL/SQL and Oracle Databases.
I need to read/write file that exists on server so i'm using utl_file.fopen('/home/tmp/','text.txt','R') but Oracle shows error 'invalid directory path'.
Main problem is that i have only user privileges, so i cant use commands like create directory user_dir as '/home/temp/' or view utl_file_dir with just show parameter utl_file_dir;
I used this code to view utl_file_dir:
SQL> set serveroutput on;
SQL> Declare
2 Intval number;
3 Strval varchar2 (500);
4 Begin
5 If (dbms_utility.get_parameter_value('utl_file_dir', intval,strval)=0)
6 Then dbms_output.put_line('value ='||intval);
7 Else dbms_output.put_line('value = '||strval);
8 End if;
9 End;
10 /
and output was 'value = 0'.
I google'd much but didnt find any solution of this problem, so i'm asking help here.
To read file i used this code:
declare
f utl_file.file_type;
s varchar2(200);
begin
f := utl_file.fopen('/home/tmp/','text.txt','R');
loop
utl_file.get_line(f,s);
dbms_output.put_line(s);
end loop;
exception
when NO_DATA_FOUND then
utl_file.fclose(f);
end;
If you do not have permission to create the directory object (and assuming that the directory object does not already exist), you'll need to send a request to your DBA (or someone else that has the appropriate privileges) in order to create a directory for you and to grant you access to that directory.
utl_file_dir is an obsolete parameter that is much less flexible than directory objects and requires a reboot of the database to change-- unless you're using Oracle 8.1.x or you are dealing with a legacy process that was written back in the 8.1.x days and hasn't been updated to use directories, you ought to ignore it.
I am using SDAC components to query a SQL Server 2008 database. It has a recordcountproperty as all datasets do and it also has the FetchAll property (which I think it is called packedrecords on clientdatasets). Said that, I got a few questions:
1 - If I set FetchAll = True the recordcount property returns ok. But in this case, when I have a large database and my query returns a lot of lines, sometimes the memory grows a lot (because it is fetching all data to get the recordcount of course).
2 - If I set FetchAll = False, the recordcount returns -1 and the memory does not grow. But I really need the recordcount. And I also wanna create a generic function for this, so I dont have to change all my existent queries.
What can I do to have the recordcount working and the memory usage of the application low in this case?
Please, do not post that I dont need recordcount (or that I should use EOF and BOF) because I really do and this is not the question.
I thought about using a query to determine the recordcount, but it has some problems since my query is going to be executed twice (1 for recordcount, 1 for data)
EDIT
#Johan pointed out a good solution, and it seems to work. Can anybody confirm this? I am using 1 TMSCconnection for every TMSQuery (because i am using threads), so I dont think this will be a problem, will it?
MSQuery1.FetchAll := False;
MSQuery1.FetchRows := 10;
MSQuery1.SQL.Text := 'select * from cidade';
MSQuery1.Open;
ShowMessage(IntToStr(MSQuery1.RecordCount)); //returns 10
MSQuery1.Close;
MSQuery2.SQL.Text := 'SELECT ##rowcount AS num_of_rows';
MSQuery2.Open;
ShowMessage(MSQuery2.FieldByName('num_of_rows').AsString); //returns 289
EDIT 2*
MSQuery1 must be closed, or MSQuery2 will not return the num_of_rows. Why is that?
MSQuery1.FetchAll := False;
MSQuery1.FetchRows := 10;
MSQuery1.SQL.Text := 'select * from cidade';
MSQuery1.Open;
ShowMessage(IntToStr(MSQuery1.RecordCount)); //returns 10
//MSQuery1.Close; <<commented
MSQuery2.SQL.Text := 'SELECT ##rowcount AS num_of_rows';
MSQuery2.Open;
ShowMessage(MSQuery2.FieldByName('num_of_rows').AsString); //returns 0
Run your query as normal, than close the query
MSQuery1.SQL.Text := 'select * from cidade';
MSQuery1.Open;
MSQuery1.Close;
You need the close otherwise SQL-server has not closed the cursor yet, and will not register the query as 'completed'.
and run the following query right afterwards:
SELECT ##rowcount AS num_of_rows
This will select the total number of rows your last select read.
It will also select the number of rows your update/delete/insert statement affected.
See: http://technet.microsoft.com/en-us/library/ms187316.aspx
Note that this variable is per connection, so queries in other connections do not affect you.
I use ODAC and I believe SDAC inherits from the same base classes and works the same way as ODAC. In ODAC, there is an option called QueryRecCount under Options in your query component. Look for TCustomDADataSet.Options.QueryRecCount in your help file.
Setting QueryRecCount = True and FetchAll = False will reduce your memory usage and give you the record count. But SDAC will run a second query in the background to get the record count so it does add a little bit of extra time to your query.
Take a look at the Devart forum entry at http://www.devart.com/forums/viewtopic.php?t=8143.