sql基础教程下载 DELPHI基础教程：SQL编程（二）[3]

DELPHI基础教程：SQL编程（二）[3]  

　　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