雙top法相比于not in和max法，就是可以傳入一條sql語(yǔ)句來(lái)生成分頁(yè)sql語(yǔ)句，也可多字段排序；

但是有利也有弊，它要求排序字段必須構(gòu)成唯一記錄，且select后的字段列表中，不允許出現(xiàn)與排序字段同名的字段。

雖然sql2k5及以上版本已經(jīng)提供了rownum()來(lái)進(jìn)行分頁(yè)處理，但是使用sql2k進(jìn)行開(kāi)發(fā)的還是較多的

using system;

using system.collections.generic;

using system.text;

/// <summary>

/// 構(gòu)造分頁(yè)后的sql語(yǔ)句

/// </summary>

public static class paginghelper

{

/// <summary>

/// 獲取分頁(yè)sql語(yǔ)句，排序字段需要構(gòu)成唯一記錄

/// </summary>

/// <param name="_recordcount">記錄總數(shù)</param>

/// <param name="_pagesize">每頁(yè)記錄數(shù)</param>

/// <param name="_pageindex">當(dāng)前頁(yè)數(shù)</param>

/// <param name="_safesql">sql查詢語(yǔ)句</param>

/// <param name="_orderfield">排序字段，多個(gè)則用“,”隔開(kāi)</param>

/// <returns>分頁(yè)sql語(yǔ)句</returns>

public static string createpagingsql(int _recordcount, int _pagesize, int _pageindex, string _safesql, string _orderfield)

{

//重新組合排序字段，防止有錯(cuò)誤

string[] arrstrorders = _orderfield.split(new char[] { ',' }, stringsplitoptions.removeemptyentries);

stringbuilder sboriginalorder = new stringbuilder(); //原排序字段

stringbuilder sbreverseo教程rder = new stringbuilder(); //與原排序字段相反，用于分頁(yè)

for (int i = 0; i < arrstrorders.length; i++)

{

arrstrorders[i] = arrstrorders[i].trim(); //去除前后空格

if (i != 0)

{

sboriginalorder.append(", ");

sbreverseorder.append(", ");

}

sboriginalorder.append(arrstrorders[i]);

int index = arrstrorders[i].indexof(" "); //判斷是否有升降標(biāo)識(shí)

if (index > 0)

{

//替換升降標(biāo)識(shí)，分頁(yè)所需

bool flag = arrstrorders[i].indexof(" desc", stringcomparison.ordinalignorecase) != -1;

sbreverseorder.appendformat("{0} {1}", arrstrorders[i].remove(index), flag ? "asc" : "desc");

}

else

{

sbreverseorder.appendformat("{0} desc", arrstrorders[i]);

}

}

//計(jì)算總頁(yè)數(shù)

_pagesize = _pagesize == 0 ? _recordcount : _pagesize;

int pagecount = (_recordcount + _pagesize - 1) / _pagesize;

//檢查當(dāng)前頁(yè)數(shù)

if (_pageindex < 1)

{

_pageindex = 1;

}

else if (_pageindex > pagecount)

{

_pageindex = pagecount;

}

stringbuilder sbsql = new stringbuilder();

//第一頁(yè)時(shí)，直接使用top n，而不進(jìn)行分頁(yè)查詢

if (_pageindex == 1)

{

sbsql.appendformat(" select top {0} * ", _pagesize);

sbsql.appendformat(" from ({0}) as t ", _safesql);

sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());

}

//最后一頁(yè)時(shí)，減少一個(gè)top n

else if (_pageindex == pagecount)

{

sbsql.append(" select * from ");

sbsql.append(" ( ");

sbsql.appendformat(" select top {0} * ", _recordcount - _pagesize * (_pageindex - 1));

sbsql.appendformat(" from ({0}) as t ", _safesql);

sbsql.appendformat(" order by {0} ", sbreverseorder.tostring());

sbsql.append(" ) as t ");

sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());

}

//前半頁(yè)數(shù)時(shí)的分頁(yè)

else if (_pageindex < (pagecount / 2 + pagecount % 2))

{

sbsql.append(" select * from ");

sbsql.append(" ( ");

sbsql.appendformat(" select top {0} * from ", _pagesize);

sbsql.append(" ( ");

sbsql.appendformat(" select top {0} * ", _pagesize * _pageindex);

sbsql.appendformat(" from ({0}) as t ", _safesql);

sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());

sbsql.append(" ) as t ");

sbsql.appendformat(" order by {0} ", sbreverseorder.tostring());

sbsql.append(" ) as t ");

sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());

}

//后半頁(yè)數(shù)時(shí)的分頁(yè)

else

{

sbsql.appendformat(" select top {0} * from ", _pagesize);

sbsql.append(" ( ");

sbsql.appendformat(" select top {0} * ", ((_recordcount % _pagesize) + _pagesize * (pagecount - _pageindex)));

sbsql.appendformat(" from ({0}) as t ", _safesql);

sbsql.appendformat(" order by {0} ", sbreverseorder.tostring());

sbsql.append(" ) as t ");

sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());

}

return sbsql.tostring();

}

/// <summary>

/// 獲取記錄總數(shù)sql語(yǔ)句

/// </summary>

/// <param name="_n">限定記錄數(shù)</param>

/// <param name="_safesql">sql查詢語(yǔ)句</param>

/// <returns>記錄總數(shù)sql語(yǔ)句</returns>

public static string createtopnsql(int _n, string _safesql)

{

return string.format(" select top {0} * from ({1}) as t ", _n, _safesql);

}

/// <summary>

/// 獲取記錄總數(shù)sql語(yǔ)句

/// </summary>

/// <param name="_safesql">sql查詢語(yǔ)句</param>

/// <returns>記錄總數(shù)sql語(yǔ)句</returns>

public static string createcountingsql(string _safesql)

{

return string.format(" select count(1) as recordcount from ({0}) as t ", _safesql);

}

}

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