DELPHI基础教程：SQL编程（二）[3]

TableOpen;

if TableActive then

TableGetFieldNames（ListBoxItems）

finally

ScreenCursor := crDefault;

end;

end;

procedure TQueryFormBitBtnClick（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 users 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 dropdown

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 { doesnt start with: NOT LIKE xx% }

soEndsWith { ends with: LIKE %xx }

soNoEndsWith { doesnt end with: NOT LIKE %xx }

soContains { contains: LIKE %xx% }

soNoContains { doesnt contain: NOT LIKE %xx% }

soBlank { is blank: }

soNotBlank { is not blank: }

soInside { contains only: IN （ xx yy zz ） }

soOutside） { doesnt contain: NOT IN （xx yy zz） }

begin

{ Initialize the variables needed to run the query }

with ListBox do

if ItemIndex = then

raise ExceptionCreate（Cant Run Query: No Alias Selected）

else

strAlias := ItemsStrings[ItemIndex];

with ListBox do

if ItemIndex = then

raise ExceptionCreate（Cant Run Query: No Table Selected）

else

strTable := ItemsStrings[ItemIndex];

with ListBox do

if ItemIndex = then

begin

if ComboBoxItemIndex > Ord（soNocondition） then

raise ExceptionCreate（Cant Run Query: No Field Selected）

else

strField := ;

end

else

strField := ItemsStrings[ItemIndex];

if （EditText = ） and

（ComboBoxItemIndex > Ord（soNoCondition）） and

（ComboBoxItemIndex < Ord（soBlank）） then

raise Exceptioncreate（Cant Run Query: No Search Value Entered）

else

strValue := EditText;

{ 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 TableFieldByName（strField） do

if （DataType = ftString） or （DataType = ftMemo） then

strQuote := else

strQuote := ;

{ Construct the WHERE clause of the query based on the users choice

in Type }

case etSQLOps（ComboBoxItemIndex） 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 ComboBoxItemIndex = Ord（soNoCondition） then

strQuery := SELECT * FROM + strTable +

else if TableFieldByName（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 := TResultFormCreate（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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