生成多字段排序分页的SQL的通用类
星期二, 06月 3rd, 2008
如果de单一字段排序分页,现在有很多de存储过程和SQL语句,分页de时候,只取pageSizede记录,可遇见de问题是:
这个单一字段必须是唯一de
这个字段必须是可以被排序de
不支持多字段排序
针对这一问题,我用C#做了一个类,解决以上de对多字段排序分页和每次都取pageSize条记录de问题 先看看相关代码:
[复制此相关代码]CODE:
using System;
using System.Collections.Specialized;
namespace web
{
/// <summary>
/// MultiOrderPagerSQL de摘要说明
/// </summary>
public class MultiOrderPagerSQL
{
private NameValueCollection orders = new NameValueCollection();
private string table_;
private string where_=”";//1=1 and 2=2 de格式
private string outfields_;
private int nowPageIndex_=0;
private int pagesize_=0;
private string sql_;//要返回deSQL
public MultiOrderPagerSQL()
{
}
/****************方法*******************/
public void addOrderField(string field, string direction)
{
orders.Add(field, direction);
}
public string getSQL()
{
//排序字段
string orderList=”";//用户期望de排序
string orderList2 = “”;//对用户期望de排序de反排序
string orderList3 = “”;//用户期望de排序,去掉了前缀.复合查询里de外层de排序不能是类似这样detable1.id,要去掉table1..
if (orders.Count > 0)
{
string[] str = orders.AllKeys;
foreach (string s in str)
{
string direction=”asc”;//默认一个方向
if (orders[s].ToString() == “asc”)
direction = “desc”;
//去掉前缀de字段名称
string s2 = “”;
int index = s.IndexOf(”.”) 1;
s2 = s.Substring(index);
orderList =orderList s ” ” orders[s] “,”;
orderList2 = orderList2 s2 ” ” direction “,”;
orderList3 = orderList3 s2 ” ” orders[s] “,”;
}
//去掉最后de,号
orderList = orderList.Substring(0,orderList.Length-1);
orderList2 = orderList2.Substring(0, orderList2.Length - 1);
orderList3 = orderList3.Substring(0, orderList3.Length - 1);
}
//return orderList2;
//形成SQL
string strTemp;
strTemp = “select * from \n ( select top {7} * from ( select top {6} {0} from {1} \n”;
if (where_ != “”)
strTemp = strTemp ” where {2} \n”;
if(orderList!=”")
strTemp = strTemp ” order by {3} ) as tmp order by {4} \n ) \n as tmp2 \n order by {5} \n”;
strTemp = string.Format(strTemp, outfields_, table_, where_, orderList, orderList2, orderList3, nowPageIndex_ * pagesize_, pagesize_);
return strTemp;
}
/****************属性*******************/
public string table
{
set { table_ = value; }
}
public string where
{
set { where_ = value; }
}
public string outfields
{
set { outfields_ = value; }
}
public int nowPageIndex
{
set { nowPageIndex_ = value; }
}
public int pagesize
{
set { pagesize_ = value; }
}
}
}
说一下原理先:其实很简单,由于AC和MS SQL 2000 没有象MS SQL 2005derow_number函数,我就不能从这里下手了,比如您取第二页,那就是序号从10-20,我先按照某一排序规则 把 前 20条de数据取出来,然后再按照先前de排序规则de反规则把这个数据反排序,再取前10条,那么这个时候就是要取de数据了,这个时候还没有结束,再把结果按照先前de排序规则排序即可.我觉得效率瓶颈会出现在排序上.看看是怎么来使用de:
[复制此相关代码]CODE:
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class MultiOrderPagerSQLTest : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
web.MultiOrderPagerSQL sql = new web.MultiOrderPagerSQL();
//sql.addOrderField(”t1.id”, “desc”);//第一排序字段
sql.addOrderField(”t1.hits”, “desc”);//第二排序字段
sql.table = “joke t1,type t2″;
sql.outfields = “t1.*,t2.type”;
sql.nowPageIndex = 5;
sql.pagesize = 10;
sql.where = “t1.typeid=t2.typeid”;
Response.Write(sql.getSQL());
}
}
以上在AC和MS SQL 2000(5)上测试通过.
暂时做出这样一个类,没有做成存储过程,要做de话,还有一点难度呢 ,呵呵.
