您可以为此创建用户定义的函数：

You can create a user-defined function for that:

CREATE FUNCTION dbo.CountUses(@pictureId INT)
RETURNS INT
AS
  BEGIN
      RETURN
        (SELECT Count(id)
         FROM   PictureUse
         WHERE  PictureId = @PictureId)
  END 

然后可以像这样添加计算列：

The computed column can then be added like this:

ALTER TABLE dbo.Picture
ADD NofUses AS dbo.CountUses(Id)

但是，我宁愿为此：

CREATE VIEW PictureView
AS
  SELECT Picture.Id,
         PictureName,
         Picture.CreateDate,
         Count(PictureUse.Id) NofUses
  FROM   Picture
         JOIN PictureUse
           ON Picture.Id = PictureUse.PictureId
  GROUP  BY Picture.Id,
            PictureName,
            Picture.CreateDate