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QBFFORM.PAS
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Pascal/Delphi Source File
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1996-05-08
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10KB
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284 lines
unit QBFForm;
interface
uses
SysUtils, Windows, Messages, Classes, Graphics, Controls,
Forms, Dialogs, StdCtrls, DB, DBTables, Buttons, ComCtrls, Tabnotbk;
type
TQueryForm = class(TForm)
BitBtn1: TBitBtn;
DataSource1: TDataSource;
Table1: TTable;
GroupBox1: TGroupBox;
CheckBox1: TCheckBox;
CheckBox2: TCheckBox;
PageControl1: TPageControl;
TabSheet1: TTabSheet;
Label5: TLabel;
Label1: TLabel;
Label2: TLabel;
Label3: TLabel;
Label4: TLabel;
ListBox1: TListBox;
ListBox2: TListBox;
ListBox3: TListBox;
Edit1: TEdit;
ComboBox1: TComboBox;
BitBtn2: TBitBtn;
TabSheet2: TTabSheet;
Memo1: TMemo;
procedure FormCreate(Sender: TObject);
procedure ListBox1Click(Sender: TObject);
procedure ListBox2Click(Sender: TObject);
procedure BitBtn2Click(Sender: TObject);
end;
var
QueryForm: TQueryForm;
implementation
{$R *.DFM}
uses RSLTFORM;
procedure TQueryForm.FormCreate(Sender: TObject);
begin
Screen.Cursor := crHourglass;
{ Populate the alias list }
with ListBox1 do
begin
Items.Clear;
Session.GetAliasNames(Items);
end;
{ Make sure there are aliases defined }
Screen.Cursor := crDefault;
if ListBox1.Items.Count < 1 then
MessageDlg( 'There are no database aliases currently defined. You ' +
'need at least one alias to use this demonstration.',
mtError, [mbOK], 0 );
{ Default the drop-down list to the first value in the list }
ComboBox1.ItemIndex := 0;
end;
procedure TQueryForm.ListBox1Click(Sender: TObject);
var
strValue: string; { Holds the alias selected by the user }
bIsLocal: Boolean; { Indicates whether or not an alias is local }
slParams: TStringList; { Holds the parameters of the selected alias }
iCounter: Integer; { An integer counter variable for loops}
begin
{ Determine the alias name selected by the user }
with ListBox1 do
strValue := Items.Strings[ItemIndex];
{ Get the names of the tables in the alias and put them in the
appropriate list box, making sure the user's choices are reflected
in the list. }
ListBox2.Items.Clear;
Session.GetTableNames(strValue, { alias to enumerate }
'', { pattern to match }
CheckBox1.Checked, { show extensions flag }
CheckBox2.Checked, { show system tables flag }
ListBox2.Items); { target for table list }
{ Make sure there are tables defined in the alias. If not, show an
error; otherwise, clear the list box. }
Screen.Cursor := crDefault;
if ListBox2.Items.Count < 1 then
MessageDlg('There are no tables in the alias you selected. Please ' +
'choose another', mtError, [mbOK], 0 );
ListBox3.Items.Clear;
end;
procedure TQueryForm.ListBox2Click(Sender: TObject);
begin
Screen.Cursor := crHourglass;
try
{ First, disable the TTable object. }
if Table1.Active then
Table1.Close;
{ Open the selected table }
with ListBox1 do
Table1.DatabaseName := Items.Strings[ItemIndex];
with ListBox2 do
Table1.TableName := Items.Strings[ItemIndex];
{ Open the table and put a list of the field names in the Fields list box. }
Table1.Open;
if Table1.Active then
Table1.GetFieldNames(ListBox3.Items);
finally
Screen.Cursor := crDefault;
end;
end;
procedure TQueryForm.BitBtn2Click(Sender: TObject);
var
strAlias, { Alias name selected by the user }
strTable, { Table name selected by the user }
strField, { Field name selected by the user }
strValue, { Field Value entered by the user }
strWhere, { WHERE clause for the user's query }
strQuote, { Holds quotes is the query field is text }
strQuery: string; { String used to construct the query }
frmQuery: TResultForm; { The Results form }
type
{ The following type is used with the Type drop-down
list. The text values corresponding with each item is
described in comments, along with the relevant SQL operators. }
etSQLOps = (soNoCondition, { not field conditions: no WHERE clause }
soEqual, { equals: = }
soNotEqual, { is not equal to: <> }
soLessThan, { is less than: < }
soLessEqual, { is less than or equal to: <= }
soMoreThan, { is greater than: > }
soMoreEqual, { is greater than or equal to: >= }
soStartsWith, { starts with: LIKE xx% }
soNoStartsWith, { doesn't start with: NOT LIKE xx% }
soEndsWith, { ends with: LIKE %xx }
soNoEndsWith, { doesn't end with: NOT LIKE %xx }
soContains, { contains: LIKE %xx% }
soNoContains, { doesn't contain: NOT LIKE %xx% }
soBlank, { is blank: }
soNotBlank, { is not blank: }
soInside, { contains only: IN ( xx, yy, zz ) }
soOutside); { doesn't contain: NOT IN (xx, yy, zz) }
begin
{ Initialize the variables needed to run the query }
with ListBox1 do
if ItemIndex = -1 then
raise Exception.Create('Can''t Run Query: No Alias Selected')
else
strAlias := Items.Strings[ItemIndex];
with ListBox2 do
if ItemIndex = -1 then
raise Exception.Create('Can''t Run Query: No Table Selected')
else
strTable := Items.Strings[ItemIndex];
with ListBox3 do
if ItemIndex = -1 then
begin
if ComboBox1.ItemIndex > Ord(soNocondition) then
raise Exception.Create('Can''t Run Query: No Field Selected')
else
strField := '';
end
else
strField := Items.Strings[ItemIndex];
if (Edit1.Text = '') and
(ComboBox1.ItemIndex > Ord(soNoCondition)) and
(ComboBox1.ItemIndex < Ord(soBlank)) then
raise Exception.create('Can''t Run Query: No Search Value Entered')
else
strValue := Edit1.Text;
{ See if the field being search is a string field. If so, then pad the
quote string with quotation marks; otherwise, set it to a null value. }
if strField <> '' then
with Table1.FieldByName(strField) do
if (DataType = ftString) or (DataType = ftMemo) then
strQuote := '"' else
strQuote := '';
{ Construct the WHERE clause of the query based on the user's choice
in Type. }
case etSQLOps(ComboBox1.ItemIndex) of
soNoCondition: strWhere := '';
soEqual: strWhere := strField + ' = ' + strQuote + strValue + strQuote;
soNotEqual: strWhere := strField + ' <> ' + strQuote + strValue + strQuote;
soLessThan: strWhere := strField + ' < ' + strQuote + strValue + strQuote;
soLessEqual: strWhere := strField + ' <= ' + strQuote + strValue + strQuote;
soMoreThan: strWhere := strField + ' > ' + strQuote + strValue + strQuote;
soMoreEqual: strWhere := strField + ' >= ' + strQuote + strValue + strQuote;
soStartsWith: strWhere := strField + ' LIKE ' + strQuote +
strValue + '%' + strQuote;
soNoStartsWith: strWhere := strField + ' NOT LIKE ' + strQuote +
strValue + '%' + strQuote;
soEndsWith: strWhere := strField + ' LIKE ' + strQuote +
'%' + strValue + strQuote;
soNoEndsWith: strWhere := strField + ' NOT LIKE ' +
strQuote + '%' + strValue + strQuote;
soContains: strWhere := strField + ' LIKE ' +
strQuote + '%' + strValue + '%' + strQuote;
soNoContains: strWhere := strField + ' NOT LIKE ' +
strQuote + '%' + strValue + '%' + strQuote;
soBlank: strWhere := strField + ' IS NULL';
soNotBlank: strWhere := strField + ' IS NOT NULL';
end;
if ComboBox1.ItemIndex = Ord(soNoCondition) then
strQuery := 'SELECT * FROM "' + strTable + '"'
else if Table1.FieldByName(strField).DataType = ftString then
strQuery := 'SELECT * FROM "' + strTable + '" t WHERE t.' + strWhere
else
strQuery := 'SELECT * FROM "' + strTable + '" t WHERE t.' + strWhere;
{ Create an instance of the browser form. }
frmQuery := TResultForm.Create(Application);
{ Use a resource protection block in case an exception is raised. This
ensures that the memory allocated for the Results form is released. }
try
with frmQuery do
begin
Screen.Cursor := crHourglass;
if Query1.Active then Query1.Close;
Query1.DatabaseName := strAlias; { set the alias the query poitns to }
Query1.SQL.clear; { empty existing SQL in the query }
Query1.SQL.Add(strQuery); { add query string to query object }
Query1.Active := True; { try to run the query }
Screen.Cursor := crDefault;
if Query1.Active then
begin
{ If the query didn't return any records, there's no point in
displaying the form. In that event, raise an exception. }
if Query1.RecordCount < 1 then
raise Exception.create('No records matched your criteria. ' +
'Please try again.' );
{ write a message to the browse form's status line }
if strField = '' then
Panel3.Caption := 'Now showing all records from ' + strTable + '...'
else
Panel3.Caption := 'Now showing ' + strTable + ' where ' +
strField + ' contains values equal to ' +
strValue + '...';
{ show the form }
ShowModal;
end;
end;
finally
frmQuery.Free;
end;
end;
end.