csharp: DataTable結構相同的比較

1        /// <summary>?        /// DataTable分頁?        /// </summary>?        /// <param name="dt">DataTable</param>?        /// <param name="PageIndex">頁索引,注意：從1開始</param>?        /// <param name="PageSize">每頁大小</param>?        /// <returns></returns>?        public static DataTable GetPagedTable(DataTable dt, int currentPageIndex, int pageSize)?        {??            //1?            //判斷當前索引?            if (currentPageIndex == 0)?                return dt;?            //從數據集合拷貝數據?            DataTable newdt = dt.Copy();?            //數據清空?            newdt.Clear();?            //開始數據索引 = 當前頁-1 x 每頁大小?            int rowbegin = (currentPageIndex - 1) * pageSize;?            //結束數據索引 = 當前頁 x 每頁大小?            int rowend = currentPageIndex * pageSize;?            //開始數據索引 大于等于 當前數據集合大小?            if (rowbegin >= dt.Rows.Count)?                return newdt;?            //結束數據索引 大于 當前數據集合大小?            if (rowend > dt.Rows.Count)?                rowend = dt.Rows.Count;?            //遍歷數據?            for (int i = rowbegin; i <= rowend - 1; i++)?            {?                DataRow newdr = newdt.NewRow();?                DataRow dr = dt.Rows[i];?                foreach (DataColumn column in dt.Columns)?                {?                    newdr[column.ColumnName] = dr[column.ColumnName];?                }?                newdt.Rows.Add(newdr);?            }??            return newdt;???            //2?            //if (currentPageIndex == 0)?            //{?            //return dt;?            //}??            //DataTable newdt = dt.Clone();// dt.Copy();??            //int rowbegin = (currentPageIndex - 1) * pageSize;//當前頁的第一條數據在dt中的位置?            //int rowend = currentPageIndex * pageSize;//當前頁的最后一條數據在dt中的位置??            //if (rowbegin >= dt.Rows.Count)?            //{?            //    return newdt;?            //}??            //if (rowend > dt.Rows.Count)?            //{?            //    rowend = dt.Rows.Count;?            //}??            //DataView dv = dt.DefaultView;?            //for (int i = rowbegin; i <= rowend - 1; i++)?            //{?            //    newdt.ImportRow(dv[i].Row);?            //}??            //return newdt;??        }??        /// <summary>2         /// DataTable 結構相同的比較?        /// ?        /// C# datatable comparison  Same  Different?        /// 涂聚文?        /// </summary>?        /// <param name="first"></param>?        /// <param name="second"></param>?        /// <returns></returns>?        public DataTable CompareTables(DataTable first, DataTable second)?        {?            first.TableName = "FirstTable";??            second.TableName = "SecondTable";??            //Create Empty Table??            DataTable table = new DataTable("Difference");??            try?            {?                //Must use a Dataset to make use of a DataRelation object?                using (DataSet ds = new DataSet())?                {?                    ds.Tables.AddRange(new DataTable[] { first.Copy(), second.Copy() });??                    //Get Columns for DataRelation??                    DataColumn[] firstcolumns = new DataColumn[ds.Tables[0].Columns.Count];???                    for (int i = 0; i < firstcolumns.Length; i++)?                    {??                        firstcolumns[i] = ds.Tables[0].Columns[i];??                    }???                    DataColumn[] secondcolumns = new DataColumn[ds.Tables[1].Columns.Count];??                    for (int i = 0; i < secondcolumns.Length; i++)?                    {??                        secondcolumns[i] = ds.Tables[1].Columns[i];??                    }???                    //Create DataRelation??                    DataRelation r = new DataRelation(string.Empty, firstcolumns, secondcolumns, false);??                    ds.Relations.Add(r);??                    //Create columns for return table??                    for (int i = 0; i < first.Columns.Count; i++)?                    {??                        table.Columns.Add(first.Columns[i].ColumnName, first.Columns[i].DataType);??                    }???                    //If First Row not in Second, Add to return table.??                    table.BeginLoadData();????                    foreach (DataRow parentrow in ds.Tables[0].Rows)?                    {??                        DataRow[] childrows = parentrow.GetChildRows(r);??                        if (childrows == null || childrows.Length == 0)??                            table.LoadDataRow(parentrow.ItemArray, true);??                    }??                    table.EndLoadData();??                }?            }?            catch (Exception ex)?            {??                throw ex;??            }??            return table;?        }

USE pubsGO--使用帶有簡單 CASE 函數的 SELECT 語句SELECT   Category =       CASE type         WHEN 'popular_comp' THEN 'Popular Computing'         WHEN 'mod_cook' THEN 'Modern Cooking'         WHEN 'business' THEN 'Business'         WHEN 'psychology' THEN 'Psychology'         WHEN 'trad_cook' THEN 'Traditional Cooking'         ELSE 'Not yet categorized'      END,   CAST(title AS varchar(25)) AS 'Shortened Title',   PRice AS PriceFROM titlesWHERE price IS NOT NULLORDER BY type, priceCOMPUTE AVG(price) BY typeGO--使用帶有簡單 CASE 函數和 CASE 搜索函數的 SELECT 語句 SELECT    'Price Category' =       CASE          WHEN price IS NULL THEN 'Not yet priced'         WHEN price < 10 THEN 'Very Reasonable Title'         WHEN price >= 10 and price < 20 THEN 'Coffee Table Title'         ELSE 'Expensive book!'      END,   CAST(title AS varchar(20)) AS 'Shortened Title'FROM titlesORDER BY priceGO--使用帶有 SUBSTRING 和 SELECT 的 CASE 函數SELECT SUBSTRING((RTRIM(a.au_fname) + ' '+    RTRIM(a.au_lname) + ' '), 1, 25) AS Name, a.au_id, ta.title_id,   Type =   CASE     WHEN SUBSTRING(ta.title_id, 1, 2) = 'BU' THEN 'Business'    WHEN SUBSTRING(ta.title_id, 1, 2) = 'MC' THEN 'Modern Cooking'    WHEN SUBSTRING(ta.title_id, 1, 2) = 'PC' THEN 'Popular Computing'    WHEN SUBSTRING(ta.title_id, 1, 2) = 'PS' THEN 'Psychology'    WHEN SUBSTRING(ta.title_id, 1, 2) = 'TC' THEN 'Traditional Cooking'  ENDFROM titleauthor ta JOIN authors a ON ta.au_id = a.au_id--