Question

我需要测试一个表是否存在于链接服务器中，其中链接服务器是一个参数（必须是），这就是我使用exec方法的原因。我尝试了很多方法，但没有成功。

Declare @LinkedServerName varchar(50)
Declare @DS varchar(50)
Declare @username varchar(50)
Declare @pswd varchar(12)
Declare @TableExists int

Set @DS = 'test\TestDB'
Set @LinkedServerName = 'LinkedServerAutoAddDrop'
Set @username = 'ua'
Set @pswd = 'pass'
Set @TableExists = 0

if not exists(select * from sys.servers where name = @LinkedServerName)
BEGIN
    EXEC sp_addlinkedserver   
       @server=@LinkedServerName, 
       @srvproduct='',
       @provider='SQLNCLI', 
       @datasrc=@DS

    EXEC sp_addlinkedsrvlogin @LinkedServerName, N'false', NULL, @username, @pswd
    exec sp_serveroption @server=@LinkedServerName, @optname='rpc', @optvalue='TRUE'
    exec sp_serveroption @server=@LinkedServerName, @optname='rpc out', @optvalue='TRUE'
END


exec('IF (EXISTS (SELECT * FROM OPENQUERY([' + @LinkedServerName + '], ''select * from LinkedDB.INFORMATION_SCHEMA.TABLES Where TABLE_NAME = ''''TableName'''''')))
BEGIN
    exec (''Set ' + @TableExists + ' = 1'')

END')

IF (@TableExists = 1)
BEGIN
    exec('Insert Into ...')
END

Answer 1

我个人会使用sp_executesql以及输出参数：

DECLARE @SQL NVARCHAR(MAX) = ''
DECLARE @TableExists BIT;

SET @SQL = 'SELECT @TableExists = CASE WHEN TableExists = 0 THEN 0 ELSE 1 END
            FROM OPENQUERY(' + QUOTENAME(@LinkedServerName) 
            + ', ''SELECT TableExists = COUNT(*) 
                    FROM LinkedDB.INFORMATION_SCHEMA.TABLES
                    WHERE TABLE_NAME = ''''TableName'''''');';

EXECUTE sp_executesql @SQL, N'@TableExists BIT OUTPUT', @TableExists OUT;

IF (@TableExists = 1)
BEGIN
    -- DO SOMETHING
END;

Answer 2

检查列是否存在我使用以下内容：

如果返回1，则COLUMN EXIST Else If 0然后COLUMN DOSE NOT EXIST

如果数据库在同一服务器上，则将@ServerName提供为空字段（＆＃39;＆＃39;）

 using System.Collections.Generic;
 using System.IO;
 using System.Linq; 
 using System.Windows;
 using System.Windows.Controls.Primitives;
 using System.Windows.Interop;
 using System.Windows.Media;
 using System.Windows.Media.Imaging;

 public class Screenshot
 {
      //UIElement to create screenshot 
      private UIElement _element;
      //Bounds for the screenshot
      private Rect _screenshotBounds;
      //Path for Screenshot
      private string _path;


      private const int DPI = 384;
      private const double BASEDPI = 96;
      private const double DPISCALE = DPI / BASISDPI;

      public Screenshot(UIElement element, string path)
      {
          this._element = element; 
          this._screenshotBounds = this.createBounds(this._element);
          this._path = path;
      }

      //public interface to create the screenshot
      public void createScreenshot()
      {
         if (this._element == null)
         {
             return;
         }
         //Create a list of tuples with the elements to render in the screenshot
         List<(UIElement, Rect, Point)> listElements = new List<(UIElement, Rect, Point)>
         {
              //Fist element in the list should be the actual UIElement
              this.createElementBoundPosition(this._element); 
         };

         RenderTargetBitmap renderBitMap = this.createBitMap(this._screenshotBounds);

         //Get the opened Popups, create a list of tuples for the Popups and add them to the list of elements to render
         listElements.AddRange(this.createListPopUpBoundsPosition( this.getOpenPopups()));

         DrawingVisual drawingVisual = this.createDrawingVisual(listElements);
         renderBitMap.Render(drawingVisual);

         this.saveRTBAsPNG(renderBitMap);
      }

      //Create DrawingVisual based on List of Tuples
      private DrawingVisual createDrawingVisual(List<(UIElement, Rect, Point)> listElements)
      {
           DrawingVisual drawingVisual = new DrawingVisual();

           using (DrawingContext context = drawingVisual.RenderOpen())
           {
                foreach((UIElement element, Rect bounds, Point position) in listElements)
                {
                      VisualBrush visualBrush = new VisualBrush(element);
                      context.DrawRectangle(visualBrush, null, new Rect(position, bounds.Size));
                }
           }

           return drawingVisual;
      }

      //Save RenderTargetBitmap to file
      private void saveRTBAsPNG(RenderTargetBitmap bitmap)
      {
          PngBitmapEncoder pngBitmapEncoder = new PngBitmapEncoder()
          {
              Interlace = PngInterlaceOption.On
          }

          pngBitmapEncoder.Frames.Add(BitmapFrame.Create(bitmap));

          using (FileStream fileStream = File.Create(this._path))
          {
              pngBitmapEncoder.Save(fileStream);
          }
      }

      //Create Bounds for Element
      private Rect createBounds(UIElement element)
      {
          new Rect(new Size((int)element.RenderSize.Width, (int)element.RenderSize.Height)); 
      } 

      //Create a Tuple with the Element, its bounds and its position
      private (UIElement element, Rect bounds, Point position) createElementBoundPosition(UIElement element)
      {
          return (element, this.createBounds(element), element.PointToScreen(new Point(0,0)));
      } 

      //create the RenderTargetBitmap
      private RenderTargetBitmap createBitMap(Rect bounds)
      {
          (int width, int height) calculatedBounds = this.calculateBounds(bounds);
           return new RenderTargetBitmap(calculatedBounds.width, calculatedBounds.height, DPI, DPI, PixelFormats.Pbgra32);
      }

      //recalculate bounds according to the scale
      private (int width, int heigth) calculateBounds(Rect bounds)
      {
          int width = (int)(bounds.Width * DPISCALE);
          int height = (int)(bounds.Height * DPISCALE);
          return (width, height);
      }

      //Convert the list of Popups into a List of Tuples
      private List<(UIElement element, Rect bounds, Point position)> createListPopUpBoundsPosition(List<Popup> listPopup)
      {
           List<(UIElement, Rect, Point)> list = new List<(UIElement, Rect, Point)>();

           foreach (Popup p in listPopup)
           {
               //The Child-Element contains the UIElement to render
               UIElement uiElement = p.Child;
               list.Add(this.createElementBoundPosition(uiElement));
           }
           return list;
      }

      //get the open Popups
      private List<Popup> getOpenPopups()
      {
           return PresentationSource.CurrentSources.OfType<HwndSource>()
               .Select(h => h.RootVisual)
               .OfType<FrameworkElement>()
               .Select(f => f.Parent)
               .OfType<Popup>()
               .Where(p => p.IsOpen).ToList();
      }

 }

如果要对表执行相同检查，请从查询中删除列部分。

测试链接服务器中是否存在表（服务器名称是参数）

2 个答案: