知识大全 SQL编程(二)[3]
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DELPHI基础教程:SQL编程(二)[3] 以下文字资料是由(全榜网网www.cha138.com)小编为大家搜集整理后发布的内容,让我们赶快一起来看一下吧!
Table Open;
if Table Active then
Table GetFieldNames(ListBox Items)
finally
Screen Cursor := crDefault;
end;
end;
procedure TQueryForm BitBtn Click(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 ments 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 ListBox do
if ItemIndex = then
raise Exception Create( Can t Run Query: No Alias Selected )
else
strAlias := Items Strings[ItemIndex];
with ListBox do
if ItemIndex = then
raise Exception Create( Can t Run Query: No Table Selected )
else
strTable := Items Strings[ItemIndex];
with ListBox do
if ItemIndex = then
begin
if ComboBox ItemIndex > Ord(soNocondition) then
raise Exception Create( Can t Run Query: No Field Selected )
else
strField := ;
end
else
strField := Items Strings[ItemIndex];
if (Edit Text = ) and
(ComboBox ItemIndex > Ord(soNoCondition)) and
(ComboBox ItemIndex < Ord(soBlank)) then
raise Exception create( Can t Run Query: No Search Value Entered )
else
strValue := Edit 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 Table 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(ComboBox 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 ComboBox ItemIndex = Ord(soNoCondition) then
strQuery := SELECT * FROM + strTable +
else if Table 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
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