ADO.NET Entity Framework(5)esql (二)

　　联合使用

myContext context = new myContext();
string esql = "SELECT Max(it.ItemValue) as Max , Min(it.ItemValue) as Min FROM myContext.DBItemList as it";
　　
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
foreach (DbDataRecord r in query)
{
Console.WriteLine("Max:{0},Min:{1}", r["Max"], r["Min"]);
}
　　
/* print:
Max:6,Min:1
*/

　　与group by一起使用

myContext context = new myContext();
string esql = "SELECT ID as ItemID , Max(it.ItemValue) as Max , Min(it.ItemValue) as Min FROM myContext.DBItemList as it group by it.ItemID as ID";
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
foreach (DbDataRecord r in query)
{
Console.WriteLine("ItemID:{0}, Max:{1},Min:{2}", r["ItemID"], r["Max"], r["Min"]);
}
　　
/* print:
ItemID:a, Max:6,Min:2
ItemID:b, Max:5,Min:1
ItemID:c, Max:6,Min:2
*/

　　数学类

　　日期

　　字符

　　esql语句 查询语句

　　CASE语句

　　CASE WHEN THEN ELSE END

myContext context = new myContext();
　　
string esql = "select it.ItemID, it.ItemValue ,(Case when it.ItemValue =1 then '差' when it.ItemValue between 2 and 4 then '好' else '其他' end) as ItemValueRemarks from myContext.DBItemList as it";
　　
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},{1},{2}", r["ItemID"], r["ItemValue"], r["ItemValueRemarks"]);
}
/*
c,4,好
c,5,其他
c,2,好
c,3,好
b,5,其他
c,6,其他
b,2,好
b,1,差
c,3,好
a,4,好
a,5,其他
a,2,好
a,3,好
a,6,其他
a,3,好
*/

　　esql 类型 简单类型

　　REF

myContext context = new myContext();
//string esql = "SELECT it.ItemID FROM DBItem as it";
string esql = "SELECT REF(it).ItemID FROM DBItem as it";
ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in v)
{
Console.WriteLine("{0}", r[0]);
}

　　ROW

myContext context = new myContext();
　　
string esql = "select value row( it.ItemValue ,it.NameID,'wxd' as wxwinter) from myContext.DBItemList as it";
　　
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},{1},{2}", r["ItemValue"], r["NameID"], r["wxwinter"]);
}

　　myContext context = new myContext();

string esql = "select row( it.ItemValue ,it.NameID) as wxd ,it.ItemID from myContext.DBItemList as it";
　　
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in query)
{
DbDataRecord v = r["wxd"] as DbDataRecord;
Console.WriteLine("{0},{1},{2}", r["ItemID"],v["ItemValue"],v["NameID"]);
}

　　集合

MULTISET(1,2,3,4)
{1,2,3,4}
SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue IN {1,2,3}

　　myContext context = new myContext();

string esql = "{1,2,3} ";
　　
ObjectQuery<int> query = context.CreateQuery<int>(esql);
　　
foreach (int r in query)
{
System.Console.WriteLine(r);
}
SELECT
[UnionAll2].[C1] AS [C1]
FROM (SELECT
　　[UnionAll1].[C1] AS [C1]
　　FROM (SELECT
　　　　1 AS [C1]
　　　　FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]
　　UNION ALL
　　　　SELECT
　　　　2 AS [C1]
　　　　FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable2]) AS [UnionAll1]
　　UNION ALL
　　　　SELECT
　　　　3 AS [C1]
　　　　FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable3]) AS [UnionAll2]

　　myContext context = new myContext();

string esql = "{row(1 as a,'wxd' as wxwinter),row(2 as a,'lzm' as wxwinter),row(3 as a,'wxwinter' as wxwinter)} ";
　　
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in query)
{
System.Console.WriteLine("{0},{1}",r["a"],r["wxwinter"]);
}
/*
1,wxd
2,lzm
3,wxwinter
*/
SELECT
1 AS [C1],
CASE WHEN ([UnionAll2].[C1] = 0) THEN 1 WHEN ([UnionAll2].[C1] = 1) THEN 2 ELSE 3 END AS [C2],
CASE WHEN ([UnionAll2].[C1] = 0) THEN 'wxd' WHEN ([UnionAll2].[C1] = 1) THEN 'lzm' ELSE 'wxwinter' END AS [C3]
FROM (SELECT
　　[UnionAll1].[C1] AS [C1]
　　FROM (SELECT
　　　　0 AS [C1]
　　　　FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]
　　UNION ALL
　　　　SELECT
　　　　1 AS [C1]
　　　　FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable2]) AS [UnionAll1]
UNION ALL
　　SELECT
　　2 AS [C1]
　　FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable3]) AS [UnionAll2]

　　Object 返回对像

　　Select 选出的值可以直接创建为对像后,将对像放入字段中返回

myContext context = new myContext();
string esql = "SELECT [WindowsFormsApplication8].[DBItemEx](it.ItemID + 'b') as myObject FROM DBItem as it";
ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in v)
{
DBItemEx obj = r["myObject"] as DBItemEx;
　　
Console.WriteLine("{0}", obj.ItemID);
　　
}

　　CAST 类型转换

myContext context = new myContext();
　　
string esql = "select value CAST(it.ItemValue as System.String) from myContext.DBItemList as it";
　　
ObjectQuery<string> query = context.CreateQuery<string>(esql);
　　
foreach (string r in query)
{
Console.WriteLine(r);
}
myContext context = new myContext();
　　
string esql = "using System;select value CAST(it.ItemValue as String) from myContext.DBItemList as it";
　　
ObjectQuery<string> query = context.CreateQuery<string>(esql);
　　
foreach (string r in query)
{
Console.WriteLine(r);
}
CAST( d as Edm.Decimal(16, 2) )

　　OFTYPE

　　OFTYPE ( expression, [ONLY] test_type )

myContext context = new myContext();
string esql = "OFTYPE(((SELECT VALUE it FROM DBItem as it) ),[WindowsFormsApplication8].[DBItemEx])";
ObjectQuery<DBItemEx> v = context.CreateQuery<DBItemEx>(esql);

　　与如下效果相同

myContext context = new myContext();
ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

　　TREAT

myContext context = new myContext();
string esql = "SELECT TREAT(it AS [WindowsFormsApplication8].[DBItemEx]) FROM DBItem AS it";
ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in v)
{
DBItemEx obj = r[0] as DBItemEx;
if (obj != null)
{
Console.WriteLine("{0}", obj.ItemID);
}
}

　　与如下效果类似

myContext context = new myContext();
ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

　　IS 类型判断

myContext context = new myContext();
string esql = "SELECT TREAT(it AS [WindowsFormsApplication8].[DBItemEx]) FROM DBItem AS it WHERE it IS OF ([WindowsFormsApplication8].[DBItemEx])";
ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);
　　
foreach (DbDataRecord r in v)
{
DBItemEx obj = r[0] as DBItemEx;
// if (obj != null)
{
Console.WriteLine("{0}", obj.ItemID);
}
}

　　与如下效果类似

myContext context = new myContext();
ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

　　esql Namespace 使用SqlServer函数

　　使用NET的数据类型

myContext context = new myContext();
　　
string esql = "using System;select value CAST(it.ItemValue as String) from myContext.DBItemList as it";
　　
ObjectQuery<string> query = context.CreateQuery<string>(esql);
　　
foreach (string r in query)
{
Console.WriteLine(r);
}
myContext context = new myContext();
　　
// ObjectQuery<typeTest> query = context.typeTest.Where("it.d==DATETIME'1977-11-11 00:00:00.000'");
ObjectQuery<typeTest> query = context.typeTest.Where("it.d==cast('1977-11-11' as System.DateTime)");
　　
foreach (typeTest r in query)
{
Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);
}

　　esql关系,导航 KEY

myContext context = new myContext();
string esql="SELECT VALUE [TargetEntity] FROM (SELECT VALUE x FROM [myContext].[FK_DBItemList_DBItem] AS x WHERE Key(x.[DBItem]) = ROW(@EntityKeyValue1 AS EntityKeyValue1)) AS [AssociationEntry] INNER JOIN [myContext].[DBItemList] AS [TargetEntity] ON Key([AssociationEntry].[DBItemList]) = Key(Ref([TargetEntity]))";
　　
ObjectQuery<DBItemList> dbitemlist = context.CreateQuery<DBItemList>(esql, new ObjectParameter("EntityKeyValue1", "a"));
　　
foreach (DBItemList r in dbitemlist)
{
Console.WriteLine("{0},{1},{2}", r.AutoId, r.ItemValue, r.NameID);
}

　　效果同下

myContext context = new myContext();
　　
ObjectQuery<DBItemList> dbitemlist = context.DBItem.First(p => p.ItemID == "a").DBItemList.CreateSourceQuery();
　　
foreach (DBItemList r in dbitemlist)
{
Console.WriteLine("{0},{1},{2}", r.AutoId, r.ItemValue, r.NameID);
}