I have a table displayed in DBGrid the sort order is based on a Sequence field and I want to be able to move an item up or down one place at a time. I have researched here and cannot find anything exactly like I need.
The problem comes when I disable the Sort order to make a change, the list reverts to the order in which the data was originally entered, so I have lost the item next in line.
This is what I have...
Folder Sequence
----------------
Buttons 1
Thread 2 << Current Row
Cotton 3
Rags 4
On clicking the "MoveDown" button I want...
Folder Sequence
----------------
Buttons 1
Cotton 2
Thread 3 << Current Row
Rags 4
But - when I remove the Sort order on Sequence I get the order I entered the items...
Folder Sequence
----------------
Buttons 1
Cotton 2
Rags 4
Thread 3 << Current Row
So far my attempts are proving pretty cumbersome and involve loading the Rows into a listbox, shuffling them and then writing them back to the Table. Gotta be a better way, but it is beyond my current grasp of SQL.
Can someone please point me in the direction to go.
I don't want to trouble anyone too much if it is a difficult thing to do in SQL, as I can always stay with the listbox approach. If it is relatively simple to an SQL-expert, then I would love to see the SQL text.
Thanks
My solution is based on the TDataSet being sorted by the Sequence field:
MyDataSet.Sort := 'Sequence';
And then swapping the Sequence field between the current row and the Next (down) / Prior (up) records e.g.:
type
TDBMoveRecord = (dbMoveUp, dbMoveDown);
function MoveRecordUpDown(DataSet: TDataSet; const OrderField: string;
const MoveKind: TDBMoveRecord): Boolean;
var
I, J: Integer;
BmStr: TBookmarkStr;
begin
Result := False;
with DataSet do
try
DisableControls;
J := -1;
I := FieldByName(OrderField).AsInteger;
BmStr := DataSet.Bookmark;
try
case MoveKind of
dbMoveUp: Prior;
dbMoveDown: Next;
end;
if ((MoveKind = dbMoveUp) and BOF) or ((MoveKind = dbMoveDown) and EOF) then
begin
Beep;
SysUtils.Abort;
end
else
begin
J := DataSet.FieldByName(OrderField).AsInteger;
Edit;
FieldByName(OrderField).AsInteger := I;
Post;
end;
finally
Bookmark := BmStr;
if (J <> -1) then
begin
Edit;
FieldByName(OrderField).AsInteger := J;
Post;
Result := True;
end;
end;
finally
EnableControls;
end;
end;
Usage:
MoveRecordUpDown(MyDataSet, 'Sequence', dbMoveDown);
// or
MoveRecordUpDown(MyDataSet, 'Sequence', dbMoveUp);
If i understand right, you want to find "next sequence item"?
May be you may do something like "get first min value, grater then X"?
In this way, you can pass prev. Row sequence value.
Related
I don't know why this function I made in pascal only gives the index of the number I'm searching for (n) and doesn't give -1 when it doesnt find it..
(i checked theres no problem with other functions the only problem is that is doesnt print the message 'num is not here' when it doesnt exist) i would also appreciate it if someone points out where my code could have been more efficient.
`
Function binary_search(L : Array Of Integer; n : Integer) : Integer;
Var
i, p, middle, first, last : Integer;
Begin
first := 0;
binary_search := -1;
last := Sizeof(L) Div Sizeof(L[0]);
While (first <= last) Do
Begin
middle := (first + last) Div 2;
If (middle = n) Then
Begin
binary_search := middle;
break;
End;
If (middle < n) Then first := middle +1;
If (middle > n) Then last := middle -1;
End;
End;
Begin
Write('num of elements in array : ');
read(m);
fillup(arr, m);
For i :=0 To m-1 Do
Begin
permutarr[i] := arr[i];
End;
Write('the num youre looking for : ');
read(A);
sort(arr, 1, m);
If (binary_search(arr, A)= -1) Then Writeln('the number isnt here') //this doesnt work
Else
Begin
For i:=0 To m-1 Do
Begin
If (permutarr[i] = binary_search(arr, A)) Then
Begin
Writeln('index : ', i);
break;
End;
End;
End;
End.
`
I am not familiar with your dialect of Pascal (it's been 15 years since I did any serious programming), but I'm quite sure that the chief problem is that
Your code is not looking at the entries of the array L at all!
All the comparisons in the function binary_search only involve the indices, middle, first, last. The first thing I would try is to edit all the comparisons with middle to use L[middle] instead (on lines 11, 16 and 17). Then your code will, at least, actually be looking at the array :-)
Other things:
I'm not 100 per cent sure that your code handles arrays of all lengths correctly (can't test right now). It might happen that first and last never meet. I'm probably wrong about this, because then your code would get stuck in an endless loop.
When I was coding I took care never to assign a value to the function_name, here binary_search prematurely. In other words, I would not be surprised to learn that your function always returns $-1$, because I fully expect the execution of a function to end the instant anything is assigned to it, so here at the line binary_search:=-1;. As I said, my dialect was different, and the recollection is "dated" at best.
Anyway, the problem in bold fits your description of the problematic behavior. You can test my theory by giving A a value that exceeds the length of the array. Then it should be unable to find it with your current code.
with dmHospital do
begin
qryHospital.SQL.Clear;
qryHospital.SQL.Add('SELECT * FROM Patients ') ;
qryHospital.SQL.Add('WHERE DoctorID = :DoctorID');
qryHospital.Parameters.ParamByName('DoctorID').Value := StrToInt(sID);
qryHospital.Open;
iCount := qryHospital.RecordCount
end;
This code displays the values I want to put into the array. However I'm not sure how to cycle through each record and to get each value from the record into the correct array. For example: I want the names from 'PatientName' and the surnames from 'PatientSurname'.
iCount is the array size.
You must loop from TDataset using While.
Some sample code:
...
var
fieldCod:TField;
Str1:String;
i, Cod:Integer;
begin
...
qryHospital.Open;
iCount := qryHospital.RecordCount;
// Create pointer to field
fieldCod := qryHospital.FieldByName('PatientCode');
// loop the recordset (while not arrive at end)
While (not qryHospital.eof) do begin
// Different modes to access table fields content
Str1 := qryHospital.FieldByName('PatientName').AsString;
i := qryHospital.Fields[1].AsInteger;
Cod := fieldCod.AsInteger;
// Add the values to your array
//...
// Next Record
qryHospital.Next;
end;
NOTE: For better performance, don't use FieldByName inside the loop (for big number of records). You can use Fields[index] or create a variable out of the loop and reference to fields.
I've been learning about the ClientDataSet in delphi and how it can help sort my SQL database. The data is showing fine in my TDBGrid and i've enabled sorting by clicking on a header by changing the IndexField of the ClientDataset. I want to make it go descending on sorts sometimes though so have been trying to use 2 IndexNames outlined here https://stackoverflow.com/a/13130816/4075632
However, when I swap the IndexName from DEFAULT_ORDER to CHANGEINDEX, all data in my DBGrid disappears. I'm pretty new to all of this, and I know it will depend on my situation, but what are some of the ways this happens and I will try to troubleshoot them.
I have 1 TSQLConnection connected to TSQLQuery, and that connected to TDataSetProvider, and that connected to my ClientDataSet which leads to a TDataSource to the TDBGrid. Why might the ClientDataSet which is usually fine cause problems when I change its name? Please bear in mind that most of the settings are default because I'm not too sure about these components. Thanks, I hope you can provide some useful help and I'm sorry it may be difficult to se my situation.
Toby
I use the following code to build indexes for a clientdataset:
Procedure BuildIndices (cds: TClientDataSet);
var
i, j: integer;
alist: tstrings;
begin
with cds do
begin
open;
logchanges:= false;
for i:= 0 to FieldCount - 1 do
if fields[i].fieldkind <> fkCalculated then
begin
j:= i * 2;
addindex ('idx' + inttostr (j), fieldlist.strings[i], [], '', '', 0);
addindex ('idx' + inttostr (j+1), fieldlist.strings[i], [ixDescending], '', '', 0);
end;
alist:= tstringlist.create;
getindexnames (alist);
alist.free;
close;
end;
end;
As a result, there is an index 'idx0' for sorting column 0 ascending and 'idx1' for sorting column 0 descending; 'idx2' and 'idx3' for column 1, etc.
Then, in the grid's OnTitleClick event, I have the following
procedure Txxx.DBGrid1TitleClick(Column: TColumn);
var
n, ex: word;
begin
n:= column.Index;
try
dbgrid1.columns[prevcol].title.font.color:= clNavy
except
end;
dbgrid1.columns[n].title.font.color:= clRed;
prevcol:= n;
directions[n]:= not directions[n];
ex:= n * 2;
if directions[n] then inc (ex);
with clientdataset do
try
disablecontrols;
indexname:= 'idx' + inttostr (ex);
finally
first;
enablecontrols
end;
end;
In each form, I define an array of booleans ('directions'), one element per grid column. These elements track whether a column should be sorted ascending or descending.
The ClientDataSet comes with two predefined indexes: DEFAULT_ORDER and CHANGEINDEX, which are of no real use for your task, because you cannot tweak them to your needs. So you have to create your own indexes. A comprehensive description by Cary Jensen can be found in this article as well as in his highly recommended book about ClientDataSets.
I've created a tabular form from a view - so only the checked items be added to a table. So far I can only insert all the records not individually selected rows.
This is the code I used:
DECLARE
v_insertcount NUMBER := 0;
BEGIN
FOR i IN 1 .. apex_application.g_f02.COUNT
LOOP
IF apex_application.g_f01 (i) IS NOT NULL THEN -- this is the checkbox
insert into my_table (pme_id, MYREF, STAC, START_DATE)
values ( SEQ_PME.NEXTVAL,
:P5_MYREF
apex_application.g_f02(i),
apex_application.g_f03(i)
)
v_insertcount := v_insertcount + 1;
END IF;
END LOOP;
END;
First you have to remember that only checked checkboxes are submitted. So you cannot test for NULL in order to identify unchecked boxes. That are simply not in the array.
So, as the checkbox array size is lower or equal to the other fields array size, you cannot use index to find corresponding values of the same row.
There are some clever tricks to overcome that limitations. However, for simple cases, a solution is simply to use a look-up function to map id to index.
FUNCTION array_search(value IN VARCHAR2, arr IN apex_application_global.vc_arr2)
RETURN PLS_INTEGER
IS
BEGIN
FOR i IN 1 .. arr.COUNT
LOOP
IF arr(i) = value THEN
RETURN i;
END IF;
END LOOP;
return 0;
END;
This is a linear search. So the performances are not very good. Anyway for form processing it is probably sufficient. Given that function, you can now write:
Region source
SELECT APEX_ITEM.CHECKBOX(1,pme_id) " ",
...
on-submit process
FOR i IN 1 .. apex_application.g_f01.COUNT -- your checkboxes
LOOP
-- identify the "row index"
idx := array_search(apex_application.g_f01(i), apex_application.g_f02);
-- ^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^
-- checkboxes array id array
-- assuming now idx > 0
-- (in production code, should check and log in case of `0`)
-- do whatever you want, using `idx` as index
insert into my_table
(pme_id,
MYREF,
STAC,
START_DATE
)
values (
SEQ_PME.NEXTVAL,
:P5_MYREF
apex_application.g_f02 (idx),
apex_application.g_f03 (idx)
);
END LOOP;
A lot of times when we query the database, we just need one column with varchar.
So I've made a nice function for querying the database and putting the results in a stringlist:
function Getdatatostringlist(sqlcomponent, sqlquery: string): TStringlist;
What I'm looking for now is basically the same function but for results with multiple columns where you don't know in advance what type the data is, be it varchar, int, datetime.
What kind of datastructure would be good to use here.
The reason I want this is that I try not to work on open datasets. I like much more to fetch all results into a temporary structure, close the dataset and work on the results.
After Kobiks reply about using in Memory datasets I came up with the following, it's fast put together to test the concept:
procedure TForm1.Button2Click(Sender: TObject);
var
MyDataSet : TAdoDataSet;
begin
MyDataSet := GetDataToDataSet('SELECT naam FROM user WHERE userid = 1', ADOConnection1);
try
Form1.Caption := MyDataSet.FieldByName('naam').AsString;
finally
MyDataSet.free;
end;
end;
function TForm1.GetDataToDataSet(sSql: string; AdoConnection: TADOConnection): TAdoDataSet;
begin
Result := TAdoDataSet.Create(nil);
Result.LockType := ltBatchOptimistic;
Result.Connection := AdoConnection;
Result.CommandText := sSql;
Result.Open;
Result.Connection := nil;
end;
I think this is something to build on.
You should use any disconnected in-memory TDataSet descendant, such as TClientDataSet.
Do not attempt to re-invent the wheel by storing a record-set in some new "Variant" structure. A TClientDataSet already contains all features you need to manipulate a "temporary" data structure.
Here is how you create a TClientDataSet structure:
cds.FieldDefs.Add('id', ftInteger);
cds.FieldDefs.Add('name', ftString, 100);
// ...
// create it
cds.CreateDataSet;
// add some data records
cds.AppendRecord([1, 'Foo']);
cds.AppendRecord([2, 'Bar']);
Many TDataSets has an ability to be used as an in-memory (client) datasets depending on the provider and LockType, for example a TADODataSet with LockType=ltBatchOptimistic could fetch results-set from the server, and then remain disconnected.
For exchanging Data with Excel this structure is usefull, might be useful for other purposes.
Function GetDatasetasDynArray(Ads: TDataset; WithHeader: Boolean = true): Variant;
// 20130118 by Thomas Wassermann
var
i, x, y: Integer;
Fields: Array of Integer;
begin
x := 0;
y := Ads.RecordCount;
if WithHeader then
inc(y);
SetLength(Fields, Ads.FieldCount);
for i := 0 to Ads.FieldCount - 1 do
if Ads.Fields[i].Visible then
begin
Fields[x] := i;
inc(x);
end;
SetLength(Fields, x);
Result := VarArrayCreate([0, y - 1 , 0, length(Fields) - 1], VarVariant);
y := 0;
if WithHeader then
begin
for i := Low(Fields) to High(Fields) do
begin
Result[y, i] := Ads.Fields[Fields[i]].DisplayLabel;
end;
inc(y);
end;
try
Ads.DisableControls;
Ads.First;
while not Ads.EOF do
begin
for i := Low(Fields) to High(Fields) do
begin
Result[y, i] := Ads.Fields[Fields[i]].Value;
end;
Ads.Next;
inc(y);
end;
finally
Ads.EnableControls;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
DynArray:Variant;
begin
DynArray := GetDatasetasDynArray(Adodataset1,true);
//DynArray[0,x] Header or First row
//DynArray[1,x] First row or SecondRow
Excel.Range.Value := DynArray;
end;
Why don't you like working with open datasets? They usually do not block the server. Copying the data from the dataset to whatever you want is extra overhead which is most likely not necessary.
A dataset provides exactly the functionality you want: A matrix with variable columns and rows.
EDIT: However, if you have iterate through the dataset often, you should consider creating a class holding the relevant information and then copy the data into a generic list, dictionary, tree or whatever you need as fast lookup structure.
Of course you could think of building something smart which can be as flexible as a dataset but: The more general things get, the poorer the performance (usually).