unitpagecut.pas

delphi做的名片管理软件

unit UnitPageCut;
interface
uses
 Windows, Messages, SysUtils, Variants, Classes, ComCtrls;
type
  TUnitPageCut = class
private
  { Private declarations }
public
   function GetMidPageIndex(pageCount:integer):integer;
   function IsAscending(orderType:string):Boolean;
   function GetSortType(ascending:Boolean):string;
   function GetPageCount(recordCount:integer;pageSize:integer):integer;
   function getSQLStr(pageIndex:integer;recordcount:integer;
pagesize:integer;queryFields:string;tablename:string;primaryKey:string;
ascending:Boolean;condition:string): string;

end;
implementation

function TUnitPageCut.getSQLStr(pageIndex:integer;recordcount:integer;
pagesize:integer;queryFields:string;tablename:string;primaryKey:string;
ascending:Boolean;condition:string): string;
var
    orderType:string;
    middleIndex:integer;
    firstIndex:integer;
    lastIndex :integer;
    pageCount:integer;
    sqlstr:string;
begin
    Result :='';
    orderType:=GetSortType(ascending);
    pageCount:=GetPageCount(recordcount,pagesize);
    middleIndex:=GetMidPageIndex(pageCount);
    firstIndex := 1;
    lastIndex := pageCount;

    if pageIndex <= firstIndex then
    begin
      Result:='select TOP '+IntToStr(PageSize)+' '+queryFields+' FROM '
        +TableName+' WHERE '+Condition+' ORDER BY '+ PrimaryKey
        +' '+orderType;
    exit;
    end;

    if (pageIndex > firstIndex) and (pageIndex <= middleIndex) then
    begin
         sqlstr:='SELECT TOP '+IntToStr(pageSize)+' '+queryFields+' FROM '+tableName
                  +' WHERE '+primaryKey;
         if ascending then
         begin
            sqlstr:=sqlstr+' > ('+' SELECT MAX(';
         end else
         begin
            sqlstr:=sqlstr+' < ('+' SELECT MIN(';
         end;
         sqlstr:=sqlstr+primaryKey+') FROM ( SELECT TOP '+
         IntToStr(pageSize*(pageIndex-1))+' '+primaryKey+' FROM '+tableName;
         if condition <> '' then
            sqlstr:=sqlstr+' WHERE '+condition+' ORDER BY '+primaryKey+' '
                  +GetSortType(ascending)+'))';
         if condition <> '' then
            sqlstr:=sqlstr+' AND '+condition+' ORDER BY '+primaryKey+' '+
                 GetSortType(ascending);
         Result:=sqlstr;
    exit;
    end;
    if (pageIndex > middleIndex) and (pageIndex < lastIndex) then
    begin

      sqlstr:='SELECT * FROM ( SELECT TOP '+IntToStr(pageSize)+' '+queryFields+' FROM '+tableName
                  +' WHERE '+primaryKey;
         if ascending then
         begin
            sqlstr:=sqlstr+' < ('+' SELECT MIN(';
         end else
         begin
            sqlstr:=sqlstr+' > ('+' SELECT MAX(';
         end;
         sqlstr:=sqlstr+primaryKey+') FROM ( SELECT TOP '+
         IntToStr(recordCount-pageSize*pageIndex)+' '+primaryKey+' FROM '+tableName;
         if condition <> '' then
            sqlstr:=sqlstr+' WHERE '+condition+' ORDER BY '+primaryKey+' ';
         if ascending then
         begin
            sqlstr:=sqlstr+' DESC)TableA)';
            if condition <> '' then
            sqlstr:=sqlstr+' and '+condition+' ORDER BY '+primaryKey+' DESC'+
                 ') TableB ORDER BY '+PrimaryKey+' ASC';
         end else
         begin
            sqlstr:=sqlstr+' ASC))';
            if condition <> '' then
            sqlstr:=sqlstr+' and '+condition+' ORDER BY '+primaryKey+' ASC'+
                 ') TableB ORDER BY '+PrimaryKey+' DESC';
         end;

         Result:=sqlstr;
     exit;
    end;

    if pageIndex >=lastIndex then
    begin
       sqlstr:='select '+queryFields+' from (select top '+
       IntToStr(recordcount-(pageCount-1)*pagesize)+' '+queryFields+' from '+
       tablename+' ';
       if condition<>'' then
          sqlstr:=sqlstr+'where '+condition+' '+'order by '+primaryKey+' ';
       if ascending then
       begin
         sqlstr:=sqlstr+'DESC)'+' order by '+primaryKey+' ';
       end else
       begin
         sqlstr:=sqlstr+'ASC)'+' order by '+primaryKey+' ';
       end;
       if ascending then
          sqlstr:=sqlstr+GetSortType(ascending);
       Result:=sqlstr;
       exit;
    end;
end;
 //---GetPageCount
function TUnitPageCut.GetPageCount(recordCount:integer;pageSize:integer):integer;
begin


    if recordCount mod pageSize>0 then
    begin
       Result:=(recordCount div pageSize)+1;
    end else
    begin
        Result:=recordCount div pageSize;
    end;
end;
//GetMidPageIndex

  function TUnitPageCut.GetMidPageIndex(pageCount:integer):integer;
  begin
       Result:=(pageCount div 2)+1;
  end;
//----GetSortType
 function TUnitPageCut.GetSortType(ascending:Boolean):string;
 begin
       Result:='DESC';
       if ascending =true then
          Result:='ASC';
 end;
//---- IsAscending
function TUnitPageCut.IsAscending(orderType:string):Boolean;
begin
      Result:=true;
     if uppercase(orderType) ='DESC' then
         Result:=false ;

end;

end.