浅谈mssql access数据库 top分页方法
但是有利也有弊，它要求排序字段必须构成唯一记录，且select后的字段列表中，不允许出现与排序字段同名的字段。 虽然sql2k5及以上版本已经提供了rownum()来进行分页处理，但是使用
<p>但是有利也有弊，它要求排序字段必须构成唯一记录，且select后的字段列表中，不允许出现与排序字段同名的字段。虽然sql2k5及以上版本已经提供了rownum()来进行分页处理，但是使用sql2k进行开发的还是较多的复制代码 代码如下:uusing system.collections.generic;sing system;using system.text;/// <summary>/// 构造分页后的sql语句/// </summary>public static class paginghelper{ /// <summary> /// 获取分页sql语句，排序字段需要构成唯一记录 /// </summary> /// <param name="_recordcount">记录总数</param> /// <param name="_pagesize">每页记录数</param> /// <param name="_pageindex">当前页数</param> /// <param name="_safesql">sql查询语句</param> /// <param name="_orderfield">排序字段，多个则用“,”隔开</param> /// <returns>分页sql语句</returns> public static string createpagingsql(int _recordcount, int _pagesize, int _pageindex, string _safesql, string _orderfield) { //重新组合排序字段，防止有错误 string[] arrstrorders = _orderfield.split(new char[] { ',' }, stringsplitoptions.removeemptyentries); stringbuilder sboriginalorder = new stringbuilder(); //原排序字段 stringbuilder sbreverseo教程rder = new stringbuilder(); //与原排序字段相反，用于分页 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]);</p>int index = arrstrorders[i].indexof(" "); //判断是否有升降标识 if (index > 0) { //替换升降标识，分页所需 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]); } }
//计算总页数 _pagesize = _pagesize == 0 ? _recordcount : _pagesize; int pagecount = (_recordcount + _pagesize - 1) / _pagesize;
//检查当前页数 if (_pageindex < 1) { _pageindex = 1; } else if (_pageindex > pagecount) { _pageindex = pagecount; }
stringbuilder sbsql = new stringbuilder(); //第一页时，直接使用top n，而不进行分页查询 if (_pageindex == 1) { sbsql.appendformat(" select top {0} * ", _pagesize); sbsql.appendformat(" from ({0}) as t ", _safesql); sbsql.appendformat(" order by {0} ", sboriginalorder.tostring()); } //最后一页时，减少一个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()); } //前半页数时的分页 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()); } //后半页数时的分页 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(); }
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