編寫基于幾個(gè)表的關(guān)聯(lián)查詢和統(tǒng)計(jì)的確是件煩瑣的事情，由于基于字符的描述很多信息難以抽取出來共用，當(dāng)其他地方需要這種情況的時(shí)候又必須重寫。為了避免這情況sql artisan引用了視圖對(duì)象，通過視圖對(duì)象描述數(shù)據(jù)查詢的信息；視圖對(duì)象有一個(gè)最大的好處就是繼承，可以從一個(gè)已經(jīng)有的對(duì)象（實(shí)體對(duì)象或視圖對(duì)象）繼承下來擴(kuò)展新的查詢功能描述。實(shí)際應(yīng)用中你可以建立一個(gè)基礎(chǔ)統(tǒng)計(jì)視圖對(duì)象，然后根據(jù)情況派生出具體的統(tǒng)計(jì)對(duì)象（如：根據(jù)不同信息分組，顯示那些字段信息等）.

下面是一些簡(jiǎn)單例程代碼：

      訂單銷售金額統(tǒng)計(jì)基礎(chǔ)視圖對(duì)象

    /// <summary>

    /// 建立一個(gè)簡(jiǎn)單的訂單銷售金額統(tǒng)計(jì)類

    /// </summary>

    [tablemap("", tabletype.view)]

    public class orderstat:hfsoft.data.itableview

    {

        #region itableview 成員

        public virtual table gettable()

        {

            // todo:  添加orderv.gettable 實(shí)現(xiàn)

            return dbmapping.orders.inner(dbmapping.employees, dbmapping.employees.employeeid)& dbmapping.orders.inner(dbmapping.orderdetails, dbmapping.orders.orderid)& dbmapping.orderdetails.inner(dbmapping.products, dbmapping.products.productid);

        }

        private double mtotalize;

        [statcolumn("quantity*[order details].unitprice*(1-discount)", stattype.sum)]

        public double totalize

        {

            get

            {

                return mtotalize;

            }

            set

            {

                mtotalize = value;

            }

        }

        #endregion

}

按雇員分組統(tǒng)計(jì)情況繼承實(shí)現(xiàn)

    /// <summary>

    /// 按雇員進(jìn)行分組統(tǒng)計(jì)

    /// </summary>

    [tablemap("", tabletype.view)]

    public class employeetotal:orderstat

    {

        private int memployeeid;

        [viewcolumn("employees.employeeid")]

        public int employeeid

        {

            get

            {

                return memployeeid;

            }

            set

            {

                memployeeid = value;

            }

        }

        private string memployeename;

        [viewcolumn("firstname+lastname")]

        public string employeename

        {

            get

            {

                return memployeename;

            }

            set

            {

                memployeename = value;

            }

        }

 }

按產(chǎn)品分組統(tǒng)計(jì)繼承實(shí)現(xiàn)

    /// <summary>

    /// 按產(chǎn)品進(jìn)行分組統(tǒng)計(jì)

    /// </summary>

    [tablemap("", tabletype.view)]

    public class producttotal : orderstat

    {

        private int mproductid;

        [viewcolumn("products.productid")]

        public int productid

        {

            get

            {

                return mproductid;

            }

            set

            {

                mproductid = value;

            }

        }

        private string mproductname;

        [viewcolumn("productname")]

        public string productname

        {

            get

            {

                return mproductname;

            }

            set

            {

                mproductname = value;

            }

        }

 }

統(tǒng)計(jì)時(shí)在不更改條件的情況，你只需要加載不同的描述類型就能實(shí)現(xiàn)不同需求的數(shù)據(jù)查詢統(tǒng)計(jì)功能。

expression exp = new expression();

exp &= new hfsoft.data.mapping.numberfield("year(" + dbmapping.orders.orderdate.name + ")", null)    == 1997;

list<employeetotal> empt= exp.list<employeetotal>();

list<producttotal> prot= exp.list<producttotal>();

關(guān)聯(lián)加載相關(guān)表信息字段

當(dāng)需要加載關(guān)聯(lián)表相關(guān)字段信息時(shí)，可以建立一個(gè)繼承于實(shí)體對(duì)象的視對(duì)象；不過也可以根據(jù)實(shí)現(xiàn)情況建立一個(gè)全新的視圖對(duì)象。

       產(chǎn)品信息視圖對(duì)象

    /// <summary>

    /// 產(chǎn)品信息視圖對(duì)象

    /// </summary>

    [tablemap("",tabletype.view)]

    public class productsview:products,hfsoft.data.itableview

    {

        #region itableview 成員

        public virtual table gettable()

        {

            return dbmapping.products.inner(dbmapping.categories, dbmapping.categories.categoryid)

                & dbmapping.products.inner(dbmapping.suppliers, dbmapping.suppliers.supplierid);

        }

        #endregion

        private string mcategoryname;

        [viewcolumn("categoryname")]

        public string categoryname

        {

            get

            {

                return mcategoryname;

            }

            set

            {

                mcategoryname = value;

            }

        }

        private string mcompanyname;

        [viewcolumn("companyname")]

        public string companyname

        {

            get

            {

                return mcompanyname;

            }

            set

            {

                mcompanyname = value;

            }

        }

}

expression exp = new expression();

    exp &= dbmapping.suppliers.city == "guangzhou";

exp.list<productsview>();

為了方便顯示，產(chǎn)品視圖對(duì)象引入了產(chǎn)品類別和供應(yīng)商信息。

以上是通過簡(jiǎn)單例程介紹sql artisan多查詢統(tǒng)計(jì)功能，組件試圖把所有數(shù)據(jù)輸出都以實(shí)體對(duì)象的方式體現(xiàn)來（主要簡(jiǎn)化訪問操作性）；不過sql artisan并沒有完全支持所有sql語(yǔ)句的功能，只是實(shí)現(xiàn)了大部常用的功能。