csharp: DataTable結構相同的比較

         
         
         
         
         
         
          DataTable GetPagedTable(DataTable dt,  currentPageIndex,  pageSize)
        {

            
             (currentPageIndex == )
                 dt;
            
            DataTable newdt = dt.Copy();
            
            newdt.Clear();
            
             rowbegin = (currentPageIndex - ) * pageSize;
            
             rowend = currentPageIndex * pageSize;
            
             (rowbegin >= dt.Rows.Count)
                 newdt;
            
             (rowend > dt.Rows.Count)
                rowend = dt.Rows.Count;
            
             ( i = rowbegin; i <= rowend - ; i++)
            {
                DataRow newdr = newdt.NewRow();
                DataRow dr = dt.Rows[i];
                 (DataColumn column  dt.Columns)
                {
                    newdr[column.ColumnName] = dr[column.ColumnName];
                }
                newdt.Rows.Add(newdr);
            }

             newdt;


            

        }

         
          
         
         
         
         
         DataTable CompareTables(DataTable first, DataTable second)
        {
            first.TableName = ;

            second.TableName = ;

            

            DataTable table =  DataTable();

            
            {
                
                 (DataSet ds =  DataSet())
                {
                    ds.Tables.AddRange( DataTable[] { first.Copy(), second.Copy() });

                    

                    DataColumn[] firstcolumns =  DataColumn[ds.Tables[].Columns.Count];


                     ( i = ; i < firstcolumns.Length; i++)
                    {

                        firstcolumns[i] = ds.Tables[].Columns[i];

                    }


                    DataColumn[] secondcolumns =  DataColumn[ds.Tables[].Columns.Count];

                     ( i = ; i < secondcolumns.Length; i++)
                    {

                        secondcolumns[i] = ds.Tables[].Columns[i];

                    }


                    

                    DataRelation r =  DataRelation(.Empty, firstcolumns, secondcolumns, );

                    ds.Relations.Add(r);

                    

                     ( i = ; i < first.Columns.Count; i++)
                    {

                        table.Columns.Add(first.Columns[i].ColumnName, first.Columns[i].DataType);

                    }


                    

                    table.BeginLoadData();



                     (DataRow parentrow  ds.Tables[].Rows)
                    {

                        DataRow[] childrows = parentrow.GetChildRows(r);

                         (childrows ==  || childrows.Length == )

                            table.LoadDataRow(parentrow.ItemArray, );

                    }

                    table.EndLoadData();

                }
            }
             (Exception ex)
            {

                 ex;

            }

             table;
        }

USE pubs
GO

--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 Price
FROM titles
WHERE price IS NOT NULL
ORDER BY type, price
COMPUTE AVG(price) BY type
GO

--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 titles
ORDER BY price
GO

--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'
  END
FROM titleauthor ta JOIN authors a ON ta.au_id = a.au_id

--