连接Access数据库，提取数据分页
假设PageSize为10，记录总数为52，则总分页数为6页。 middleIndex=2,firstIndex=0,lastIndex=5.
pageIndex= 0 进第一页
pageIndex=1 进前半段
pageIndex= 3 进后半段
pageIndex= 5 进最后
核心代码段：
/***查询语句***/#region/***查询语句***/
/**//// <summary>
/// 获取根据指定字段排序并分页查询的 SELECT 语句。 /// </summary> /// <param name="pageSize">每页要显示的记录的数目。</param> /// <param name="pageIndex">要显示的页的索引。</param> /// <param name="recordCount">数据表中的记录总数。</param> /// <param name="tableName">要查询的数据表。</param> /// <param name="queryFields">要查询的字段。</param> /// <param name="primaryKey">主键字段。</param> /// <param name="ascending">是否为升序排列。</param> /// <param name="condition">查询的筛选条件。</param>
/// <returns>返回排序并分页查询的 SELECT 语句。</returns> public static String Paging( int pageSize, int pageIndex, int recordCount, String tableName, String queryFields, String primaryKey, bool ascending, String condition ) 
{ 实现#region 实现 StringBuilder sb = new StringBuilder(); int pageCount = GetPageCount(recordCount,pageSize); //分页的总数 int middleIndex = GetMidPageIndex(pageCount); //中间页的索引 int firstIndex = 0; //第一页的索引 int lastIndex = pageCount - 1; //最后一页的索引 @PageIndex = @FirstIndex#region @PageIndex <= @FirstIndex //Top @PageSize取到第一页要显示的记录 select top @PageSize @QueryFields Form @TableName WHERE @Condition --ORDER BY @PrimaryKey ASC if (pageIndex <= firstIndex) { sb.Append("SELECT TOP ").Append(pageSize).Append(" ").Append(queryFields) .Append(" FROM ").Append(tableName); if (condition != String.Empty) sb.Append(" WHERE ").Append(condition); sb.Append(" ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(ascending)); } #endregion @FirstIndex @PageIndex = @MiddleIndex#region @FirstIndex < @PageIndex <= @MiddleIndex //取前半部分记录的SQL语句。 先取出当前页之前 的所有记录的主键值，再从中选出最大值，然后取出主键值 > 该最大值的前@PageSize条记录。 // select top @PageSize @QueryFields from @TableName where @PrimaryKey>( //select Max(@PrimaryKey) from //(select top @PageSize*@PageIndex @PrimaryKey from @TableName where @Condition) TableA //) where @Condition else if (pageIndex > firstIndex && pageIndex <= middleIndex) { sb.Append("SELECT TOP ").Append(pageSize).Append(" ").Append(queryFields) .Append(" FROM ").Append(tableName) .Append(" WHERE ").Append(primaryKey); if (ascending) sb.Append(" > (").Append(" SELECT MAX("); else sb.Append(" < (").Append(" SELECT MIN("); sb.Append(primaryKey).Append(") FROM ( SELECT TOP ") .Append(pageSize*pageIndex).Append(" ").Append(primaryKey) .Append(" FROM ").Append(tableName); if (condition != String.Empty) sb.Append(" WHERE ").Append(condition); sb.Append(" ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(ascending)) .Append(" ) TableA )"); if (condition != String.Empty) sb.Append(" AND ").Append(condition); sb.Append(" ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(ascending)); } #endregion @MiddleIndex @PageIndex @LastIndex#region @MiddleIndex < @PageIndex < @LastIndex //取数据表后半部分记录的sql语句。先取出当前页之后的所有记录的主键值，再从中选出最小值，然后取出主键值 <该最小值 的前@PageSize条记录。 //select * from(select Top @PageSize @QueryFields From @TableName where @PrimaryKey <( //select min(@PrimaryKey) from ( //select top (@RecordCount-@PageSize*(@PageIndex+1)) @PrimaryKey from @TableName where Condition order by @primaryKey DESC ) TableA //) where @Condition order by @primaryKey DESC) TableB Order by @Primarykey ASC else if (pageIndex > middleIndex && pageIndex < lastIndex) { sb.Append("SELECT * FROM ( SELECT TOP ") .Append(pageSize).Append(" ").Append(queryFields) .Append(" FROM ").Append(tableName) .Append(" WHERE ").Append(primaryKey); if (ascending) sb.Append(" < (").Append(" SELECT MIN("); else sb.Append(" > (").Append(" SELECT MAX("); sb.Append(primaryKey).Append(") FROM ( SELECT TOP ") .Append(recordCount-pageSize*(pageIndex+1)).Append(" ").Append(primaryKey) .Append(" FROM ").Append(tableName); if (condition != String.Empty) sb.Append(" WHERE ").Append(condition); sb.Append(" ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(!ascending)) .Append(" ) TableA )"); if (condition != String.Empty) sb.Append(" AND ").Append(condition); sb.Append(" ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(!ascending)) .Append(" ) TableB ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(ascending)); } #endregion @PageIndex = @LastIndex#region @PageIndex >= @LastIndex //取最后一页的记录时要先计算出该页的记录数，作为Top语句的条件，而不能直接用Top @PageSize ,这样取出来的记录 并不只是 最后一页的。其实很多网站确实这样做。 //select * from( //select top (@RecordCount -@PageSize*@LastIndex) @QueryFields From @TableName Where @Condition Order by @PrimaryKey DESC // ) TableA order by @Primarykey ASC else if (pageIndex >= lastIndex) { sb.Append("SELECT * FROM ( SELECT TOP ").Append(recordCount-pageSize*lastIndex) .Append(" ").Append(queryFields) .Append(" FROM ").Append(tableName); if (condition != String.Empty) sb.Append(" WHERE ").Append(condition); sb.Append(" ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(!ascending)) .Append(" ) TableA ORDER BY ").Append(primaryKey).Append(" ") .Append(GetSortType(ascending)); } #endregion return sb.ToString(); #endregion }
#endregion