csharp: DataTable结构相同的比较
时间：2014-03-11 01:06:52
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1 /// <summary>? /// DataTable分页? /// </summary>? /// <param name="dt">DataTable</param>? /// <param name="PageIndex">页索引,注意：从1开始</param>? /// <param name="PageSize">每页大小</param>? /// <returns></returns>? public static DataTable GetPagedTable(DataTable dt, int currentPageIndex, int pageSize)? {?? //1? //判断当前索引? if (currentPageIndex == 0)? return dt;? //从数据集合拷贝数据? DataTable newdt = dt.Copy();? //数据清空? newdt.Clear();? //开始数据索引 = 当前页-1 x 每页大小? int rowbegin = (currentPageIndex - 1) * pageSize;? //结束数据索引 = 当前页 x 每页大小? int rowend = currentPageIndex * pageSize;? //开始数据索引 大于等于 当前数据集合大小? if (rowbegin >= dt.Rows.Count)? return newdt;? //结束数据索引 大于 当前数据集合大小? if (rowend > dt.Rows.Count)? rowend = dt.Rows.Count;? //遍历数据? 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;//当前页的第一条数据在dt中的位置? //int rowend = currentPageIndex * pageSize;//当前页的最后一条数据在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 结构相同的比较? /// ? /// 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;? }
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USE pubsGO--使用带有简单 CASE 函数的 SELECT 语句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--使用带有简单 CASE 函数和 CASE 搜索函数的 SELECT 语句 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--使用带有 SUBSTRING 和 SELECT 的 CASE 函数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-- |
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原文：http://www.cnblogs.com/geovindu/p/3592347.html
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