SQL server 多表联合查询

//返回的数据类型为DataTable，DataTable 比较灵活，
//如果有更新操作，字段不不定的，比较合适。而不是list<string>
public DataTable GetProjectMessage(int projectSupervisionUnit)
        {
            projectSupervisionUnit = 10001;//上海市卫生管理局，这里我是写的一个死数据用来测试
           //这里注意，之前我把foreach包裹using，报了一个bug，
           //自己没有仔细去想，using会创建数据库连接，
           //如果多次查询多次连接数据库，肯定是不对的。被人看到，笑掉大牙了。
            using (EF.MSISEntities context = new EF.MSISEntities())
            {
                //根据当前的监管单位，查到监管单位下所属的项目，得到项目ids
                var item = context.Project_SupervisionUnit.Where(o => o.SupervisionUnit_Id == projectSupervisionUnit).ToList();

                context.Database.CommandTimeout = 9999;
                DataTable ds = new DataTable();
                foreach (var i in item)
                {
                //这里是想一个sql语句查询出项目名称，项目负责人，创建日期，该项目的病例数，该项目的表单数，
                //因此用的子查询，但是注意子查询的结果不能返回多条，负责报错。我这里的子查询根据id来查，因此只有一个结果不会报错。
                //另外实际项目中最好起有意思的名字，什么p1,p2显得极为不专业
                    var testCommand = new SqlCommand(@"SELECT  DISTINCT  p1.Name, p1.OwnerUserCode, p1.CreateDate,
                    (SELECT   COUNT(DISTINCT p3.Patient_Id) AS Patient_IdSUM
                     FROM    Project AS p1 INNER JOIN
                     PatientGroup AS p2 ON p1.Id = p2.Project_Id INNER JOIN
                     PatientInGroup AS p3 ON p2.Id = p3.PatientGroup_Id
                     WHERE   (p1.Id  =@id)) AS Patient_IdSUMS,
                    (SELECT   COUNT(DISTINCT CRFForm_Id) AS CRFForm_IdSUM
                     FROM      CRF_Variable
                     WHERE   (Project_Id =@id)) AS CRFForm_IdSUMS
FROM      Project AS p1 INNER JOIN
                PatientGroup AS p2 ON p1.Id = p2.Project_Id INNER JOIN
                PatientInGroup AS p3 ON p2.Id = p3.PatientGroup_Id
WHERE   (p1.Id =@id)", (SqlConnection)context.Database.Connection);

                testCommand.Parameters.Add("@id", SqlDbType.Int); 
                testCommand.Parameters["@id"].Value = i.Project_Id;
                //testCommand.Parameters.AddWithValue("@id", );
                SqlDataAdapter adapter = new SqlDataAdapter(testCommand);

                    adapter.Fill(ds);

                }

                return ds;

            }
        }
SQL server 多表联合查询

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