分頁查詢總結

  分頁查詢總結
  oracle的分頁是先進行查詢並排序，而後在經過rownum進行範圍截取，而且要排序
  內存分頁要本身對查詢結果進行排序，而後經過index進行範圍截取
  重要的點是，首先要知道總的查詢結果數量totalNum，根據每頁大小pageSize，計算出總頁數totalPage，本頁結果數量curNum,
  根據當前頁curPage和每頁大小pageSize獲得須要截取的範圍startIndex和endIndex
  1.totalNum
  2.pageSize、curPage
  3.startIndex、endIndex
  4.curNum
  5.計算公式:
  a.startIndex=pageSize*(curPage-1)+1 
  b.endIndex=startIndex + pageSize - 1
  c.totalPage=(totalNum-1)/pageSize + 1

 

 

oracle分頁樣本：

總數：

ResultSet sets = stmt.executeQuery("select count(1) from ("+sql+")");
   if(sets.next()){
    totalNum = sets.getInt(1);
   }

分頁結果：

StringBuffer buff = new StringBuffer(256);
   
   int startIndex = pageSize * (curPage - 1) + 1;
   int endIndex = startIndex + pageSize - 1;
   
   buff.append("select * from (");
   buff.append("select b.*,rownum row_num from (");
   buff.append("select * from (" + sql + ") a order by " + orderBy);
   buff.append(") b");
   buff.append(") c where row_num between " + startIndex + " and "
     + endIndex + " order by " + orderBy);