ADO.NET Entity Framework(5)esql
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目录
1????esql的查询结果集 ObjectQuery????1
1.1????ObjectQuery<实体>????1
1.2????ObjectQuery<DbDataRecord>????1
1.3????ObjectQuery<简单类型>????1
2????esql的使用????2
2.1????it关键字????2
2.2????value 关键字????2
2.3????查询参数的使用????3
2.4????中文字段????3
3????得到esql与sql字串????3
3.1????CommandText属性????4
3.2????ToTraceString方法????4
4????ObjectQuery的Linq方法????4
4.1????Where????4
4.2????OrderBy????4
4.3????Select????4
4.4????SelectValue(projection)????4
4.5????Top(count)????5
4.6????Skip(keys,count)????5
4.7????分页 Skip Top????5
4.8????GroupBy(keys,projection)????6
4.9????Include(path)????6
5????esql注释,成员访问,分行????6
6????esql运算符????7
6.1????算术运算符????7
6.2????比效运算符????7
6.3????逻辑运算符????7
6.4????区间????7
6.5????集合运算????8
7????esql函数????10
7.1????统计类????10
7.1.1????联合使用????11
7.1.2????与group by一起使用????11
7.2????数学类????11
7.3????日期????11
7.4????字符????12
8????esql语句????12
8.1????查询语句????12
8.2????CASE语句????14
9????esql 类型????14
9.1????简单类型????14
9.2????REF????16
9.3????ROW????16
9.4????集合????16
9.5????Object 返回对像????17
9.6????CAST 类型转换????17
9.7????OFTYPE????18
9.8????TREAT????18
9.9????IS 类型判断????19
10????esql Namespace????19
10.1????使用SqlServer函数????19
10.2????使用NET的数据类型????20
11????esql关系,导航????20
11.1????KEY????20
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比起 LINQ to SQL，EF 除了提供 LINQ 查询方式,还提供了 Entity SQL language
ESQL 类似 Hibernate 的 HSQL，ESQL 与SQL 语言的语法相似，以字符串的方式执行
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esql的查询结果集 ObjectQuery
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ObjectQuery<实体>
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myContext context = new myContext();
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string esql = "SELECT VALUE DBItemList FROM myContext.DBItemList";
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// ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql,context);
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine(r.NameID);
}
myContext context = new myContext();
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string esql = "SELECT VALUE it FROM myContext.DBItemList as it";
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// ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql,context);
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine(r.NameID);
}
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ObjectQuery<DbDataRecord>
myContext context = new myContext();
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string esql = "SELECT it.NameID FROM myContext.DBItemList as it";
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//ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esql,context);
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
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foreach (DbDataRecord r in query)
{
Console.WriteLine(r["NameID"].ToString());
}
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ObjectQuery<简单类型>
myContext context = new myContext();
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string esql = "SELECT value count(it.NameID) FROM myContext.DBItemList as it";
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// ObjectQuery<int> query = new ObjectQuery<int>(esql,context);
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ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
myContext context = new myContext();
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string esql = "SELECT value it.NameID FROM myContext.DBItemList as it";
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// ObjectQuery<int> query = new ObjectQuery<int>(esql,context);
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ObjectQuery<string> query = context.CreateQuery<string>(esql);
foreach (string n in query)
{
Console.WriteLine(n);
}
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esql的使用
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可以在
- ObjectQuery的Linq方法,
- 构造ObjectQuery,
- context.CreateQuery返方法,
中使用esql,并得到返回的榄查询结果ObjectQuery
it关键字
[it] 出现在 ESQL 中,由 ObjectQuery<T>.Name 属性设定，用于标示源查询对象(ObjectQuery)的名称，
类似于 "SELECT * FROM Tab as it WHERE it.ItemValue =14" 。
可以将这个默认值 "it" 改成其他字符串。
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myContext context = new myContext();
context.DBItemList.Name = "wxd";
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ObjectQuery<DBItemList> list = context.DBItemList.Where("wxd.ItemValue=5");
myContext context = new myContext();
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var sql = "SELECT VALUE DBItemList FROM myContext.DBItemList";
var query = new ObjectQuery<DBItemList>(sql,context);
query.Name = "wxd";
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ObjectQuery<DBItemList> list = query.Where("wxd.ItemValue=@v",new ObjectParameter("v",5));
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value 关键字
value 后只能返回一个成员
myContext context = new myContext();
string esql = "SELECT value AVG(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
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/* print:
3
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string esql = "select value it.ItemID from myContext.DBItemList as it";
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ObjectQuery<string> query = context.CreateQuery<string>(esql);
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foreach (string r in query)
{
Console.WriteLine(r);
}
myContext context = new myContext();
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string esql = "select value row( it.ItemValue,it.NameID,'wxd' as wxwinter) from myContext.DBItemList as it";
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ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
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foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},{1},{2}",r["ItemValue"],r["NameID"],r["wxwinter"]);
}
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查询参数的使用
myContext context = new myContext();
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string esql = "SELECT VALUE it FROM myContext.DBItemList as it where it.ItemValue=@v1 or it.NameID=@v2";
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ObjectParameter v1 = new ObjectParameter("v1",3);
ObjectParameter v2 = new ObjectParameter("v2","n01");
ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql,v1,v2);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},{1}",r.NameID,r.ItemValue);
}
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中文字段
使用[]将字段括起来
myContext context = new myContext();
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ObjectQuery<typeTest> query = context.typeTest.Where("it.值 ==22.22");
System.Console.WriteLine(query.CommandText);
foreach (typeTest r in query)
{
Console.WriteLine("{0},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);
}
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myContext context = new myContext();
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ObjectQuery<typeTest> query = context.typeTest.Where("it.[值] ==22.22");
System.Console.WriteLine(query.CommandText);
foreach (typeTest r in query)
{
Console.WriteLine("{0},r.值);
}
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得到esql与sql字串
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myContext context = new myContext();
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string esql = "SELECT VALUE it FROM myContext.DBItemList as it";
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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Console.WriteLine(query.CommandText);
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Console.WriteLine(query.ToTraceString())
SELECT VALUE it FROM myContext.DBItemList as it
SELECT
[Extent1].[AutoId] AS [AutoId],
[Extent1].[NameID] AS [NameID],
[Extent1].[ItemID] AS [ItemID],
[Extent1].[ItemValue] AS [ItemValue]
FROM [dbo].[DBItemList] AS [Extent1]
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CommandText属性
得到esql字串
ToTraceString方法
得到sql字串
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ObjectQuery的Linq方法
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Where
用字符串为条件进行查询
ObjectQuery<T> Where(string predicate,params ObjectParameter[] parameters);
myContext context = new myContext();
ObjectQuery<DBItemList> list = context.DBItemList.Where("(it.ItemValue=5 or it .ItemValue=5) and it.NameID='n01'");
SELECT
[Extent1].[AutoId] AS [AutoId],
[Extent1].[NameID] AS [NameID],
[Extent1].[ItemID] AS [ItemID],
[Extent1].[ItemValue] AS [ItemValue]
FROM [dbo].[DBItemList] AS [Extent1]
WHERE (([Extent1].[ItemValue] = 5) OR ([Extent1].[ItemValue] = 5)) AND ([Extent1].[NameID] = 'n01')
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OrderBy
排序
ObjectQuery<T> OrderBy(string keys,params ObjectParameter[] parameters);
myContext context = new myContext();
ObjectQuery<DBItemList> query = context.DBItemList.OrderBy("it.ItemValue,it.ItemID desc");
foreach (var r in query)
{
Console.WriteLine("{0},{3}",r.AutoId,r.ItemID,r.ItemValue);
}
SELECT
[Extent1].[AutoId] AS [AutoId],
[Extent1].[ItemValue] AS [ItemValue]
FROM [dbo].[DBItemList] AS [Extent1]
ORDER BY [Extent1].[ItemValue] ASC, [Extent1].[ItemID] DESC
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Select
射影
ObjectQuery<DbDataRecord> Select(string projection,params ObjectParameter[] parameters);
myContext context = new myContext();
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ObjectQuery<DbDataRecord> list = context.DBItemList.Select(" it.ItemValue as a,it.NameID ");
SELECT
1 AS [C1],
[Extent1].[ItemValue] AS [ItemValue],
[Extent1].[NameID] AS [NameID]
FROM [dbo].[DBItemList] AS [Extent1]
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SelectValue(projection)
返回只有一组字段的数组
ObjectQuery<TResultType> SelectValue<TResultType>(string projection,params ObjectParameter[] parameters);
myContext context = new myContext();
ObjectQuery<int> query = context.DBItemList.SelectValue<int>("it.ItemValue + it.AutoID");
foreach (var r in query)
{
Console.WriteLine(r);
}
SELECT
[Extent1].[ItemValue] + [Extent1].[AutoId] AS [C1]
FROM [dbo].[DBItemList] AS [Extent1]
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Top(count)
集合的前n个元素
count : 前n个元素
ObjectQuery<T> Top(string count,params ObjectParameter[] parameters);
myContext context = new myContext();
ObjectQuery<DBItemList> query = context.DBItemList.Top("3"); ;
foreach (var r in query)
{
Console.WriteLine("{0},r.ItemValue);
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}
SELECT TOP (3)
[c].[AutoId] AS [AutoId],
[c].[NameID] AS [NameID],
[c].[ItemID] AS [ItemID],
[c].[ItemValue] AS [ItemValue]
FROM [dbo].[DBItemList] AS [c]
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Skip(keys,count)
跳过集合的前n个元素,
keys : 用于排序的字段
count : 要跳过的记录个数
ObjectQuery<T> Skip(string keys,string count,params ObjectParameter[] parameters);
myContext context = new myContext();
ObjectQuery<DBItemList> query = context.DBItemList.Skip("it.ItemValue","5");
foreach (var r in query)
{
Console.WriteLine("{0},r.ItemValue);
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}
SELECT
[Extent1].[AutoId] AS [AutoId],
[Extent1].[ItemValue] AS [ItemValue]
FROM ( SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS [NameID], [Extent1].[ItemID] AS [ItemID], [Extent1].[ItemValue] AS [ItemValue], row_number() OVER (ORDER BY [Extent1].[ItemValue] ASC) AS [row_number]
????FROM [dbo].[DBItemList] AS [Extent1]
) AS [Extent1]
WHERE [Extent1].[row_number] > 5
ORDER BY [Extent1].[ItemValue] ASC
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分页 Skip Top
Skip与Top一起使用
myContext context = new myContext();
ObjectQuery<DBItemList> query = context.DBItemList.Skip("it.ItemValue","5").Top("3"); ;
foreach (var r in query)
{
Console.WriteLine("{0},r.ItemValue);
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}
SELECT TOP (3)
[Extent1].[AutoId] AS [AutoId], row_number() OVER (ORDER BY [Extent1].[ItemValue] ASC) AS [row_number]
????FROM [dbo].[DBItemList] AS [Extent1]
) AS [Extent1]
WHERE [Extent1].[row_number] > 5
ORDER BY [Extent1].[ItemValue] ASC
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GroupBy(keys,projection)
分组
keys: GROUP BY的字段
projection : Select 的内容
ObjectQuery<DbDataRecord> GroupBy(string keys,string projection,params ObjectParameter[] parameters);
myContext context = new myContext();
ObjectQuery<DbDataRecord> query = context.DBItemList.GroupBy("it.ItemID","it.ItemID,Sum(it.ItemValue) as ValueSum");
foreach (var r in query)
{
Console.WriteLine("{0},r["ItemID"],r["ValueSum"]);
}
/*
a,23
b,8
c,23
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SELECT
1 AS [C1],
[GroupBy1].[K1] AS [ItemID],
[GroupBy1].[A1] AS [C2]
FROM ( SELECT
????[Extent1].[ItemID] AS [K1],
????SUM([Extent1].[ItemValue]) AS [A1]
????FROM [dbo].[DBItemList] AS [Extent1]
????GROUP BY [Extent1].[ItemID]
) AS [GroupBy1]
SELECT it.ItemID,Sum(it.ItemValue) as ValueSum
FROM ( [DBItemList] ) AS it
GROUP BY it.ItemID
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Include(path)
加载关联数据,参数为实体的[导航属性]的字串,调用Include("导航属性")后,关联数据会加载,这样就不用在[实体.导航属性]上调用Load()方法
ObjectQuery<T> Include(string path);
myContext context = new myContext();
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var r = context.DBItem.Include("DBItemList");
foreach (var dbitem in r)
{
foreach (var dbitemlist in dbitem.DBItemList)
{
Console.WriteLine("{0},dbitemlist.NameID,dbitemlist.ItemValue);
}
}
效果与下例相同
myContext context = new myContext();
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var r = context.DBItem;
foreach (var dbitem in r)
{
dbitem.DBItemList.Load();
foreach (var dbitemlist in dbitem.DBItemList)
{
Console.WriteLine("{0},dbitemlist.ItemValue);
}
}
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esql注释,分行
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注释
--
成员访问
.
分行
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esql运算符
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算术运算符
加
+
减
-
乘
*
除
/
模
%
负
-
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比效运算符
等于
=
大于
>
大于等于
>=
空判断
IS NOT NULL
IS NULL
小于
<
小天等于
<=
不等于
!=
<>
字符比效
LIKE ''
NOT LIKE ''
% :
_ :
[ ] :
[^] :
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逻辑运算符
与
AND
&&
非
NOT
!
或
OR
||
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区间
BETWEEN
之间
BETWEEN n AND m
NOT BETWEEN n AND m
myContext context = new myContext();
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string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue BETWEEN 2 and 4";
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
myContext context = new myContext();
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ObjectQuery<DBItemList> query = context.DBItemList.Where(" it.ItemValue not BETWEEN 2 and 4");
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
IN
在集合中
IN {v,v}
NOT IN{v,v}
myContext context = new myContext();
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string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue IN {1,2,3}";
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
myContext context = new myContext();
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ObjectQuery<DBItemList> query = context.DBItemList.Where("it.ItemValue not IN {1,3}");
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
EXISTS
存在
EXISTS(select from)
NOT EXISTS(select from)
myContext context = new myContext();
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string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE exists(Select VALUE it2 From DBItem as it2 Where it2.ItemID=it.ItemID )";
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
myContext context = new myContext();
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ObjectQuery<DBItemList> query = context.DBItemList.Where("exists(Select VALUE it2 From DBItem as it2 Where it2.ItemID=it.ItemID )");
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
分页
SELECT VALUE it FROM ( [DBItemList] ) AS it
ORDER BY it.ItemValue
SKIP 5
LIMIT 3
集合运算
Union
(合集)
连接不同集合
UNION --自动过滤相同项
UNION ALL --两个集合的相同项都会返回
myContext context = new myContext();
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string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ) UNION (select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' )";
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ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
EXCEPT
(左并集)
从集合中删除其与另一个集合中相同的项
myContext context = new myContext();
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string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ) EXCEPT (select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' )";
ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
INTERSECT
（交集）
获取不同集合的相同项
myContext context = new myContext();
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string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ) INTERSECT (select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' )";
ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
ANYELEMENT
集合中的第一个
myContext context = new myContext();
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string esql = "ANYELEMENT(select value it from myContext.DBItemList as it where it.ItemID == 'a') ";
ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
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//如果集合中有两个以上,只返回第一个到集合中
foreach (DBItemList r in query)
{
Console.WriteLine("{0},r.ItemValue);
}
SELECT
[Element1].[AutoId] AS [AutoId],
[Element1].[NameID] AS [NameID],
[Element1].[ItemID] AS [ItemID],
[Element1].[ItemValue] AS [ItemValue]
FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]
LEFT OUTER JOIN (SELECT TOP (1)
????[Extent1].[AutoId] AS [AutoId],
????[Extent1].[NameID] AS [NameID],
????[Extent1].[ItemID] AS [ItemID],
????[Extent1].[ItemValue] AS [ItemValue]
????FROM [dbo].[DBItemList] AS [Extent1]
????WHERE [Extent1].[ItemID] = 'a' ) AS [Element1] ON 1 = 1
OVERLAPS
两个集合是否有相交部份
myContext context = new myContext();
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string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID=='b' ) OVERLAPS (select value it from myContext.DBItemList as it where it.ItemID == 'a' || it.ItemID=='b')";
ObjectQuery<bool> query = context.CreateQuery<bool>(esql);
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foreach (bool r in query)
{
Console.WriteLine(r);
}
//print: True
SELECT
CASE WHEN ( EXISTS (SELECT
????cast(1 as bit) AS [C1]
????FROM (SELECT
????????[Extent1].[AutoId] AS [AutoId],
????????[Extent1].[NameID] AS [NameID],
????????[Extent1].[ItemID] AS [ItemID],
????????[Extent1].[ItemValue] AS [ItemValue]
????????FROM [dbo].[DBItemList] AS [Extent1]
????????WHERE ([Extent1].[ItemID] = 'c') OR ([Extent1].[ItemID] = 'b')
????INTERSECT
????????SELECT
????????[Extent2].[AutoId] AS [AutoId],
????????[Extent2].[NameID] AS [NameID],
????????[Extent2].[ItemID] AS [ItemID],
????????[Extent2].[ItemValue] AS [ItemValue]
????????FROM [dbo].[DBItemList] AS [Extent2]
????????WHERE ([Extent2].[ItemID] = 'a') OR ([Extent2].[ItemID] = 'b')) AS [Intersect1]
)) THEN cast(1 as bit) WHEN ( NOT EXISTS (SELECT
????cast(1 as bit) AS [C1]
????FROM (SELECT
????????[Extent3].[AutoId] AS [AutoId],
????????[Extent3].[NameID] AS [NameID],
????????[Extent3].[ItemID] AS [ItemID],
????????[Extent3].[ItemValue] AS [ItemValue]
????????FROM [dbo].[DBItemList] AS [Extent3]
????????WHERE ([Extent3].[ItemID] = 'c') OR ([Extent3].[ItemID] = 'b')
????INTERSECT
????????SELECT
????????[Extent4].[AutoId] AS [AutoId],
????????[Extent4].[NameID] AS [NameID],
????????[Extent4].[ItemID] AS [ItemID],
????????[Extent4].[ItemValue] AS [ItemValue]
????????FROM [dbo].[DBItemList] AS [Extent4]
????????WHERE ([Extent4].[ItemID] = 'a') OR ([Extent4].[ItemID] = 'b')) AS [Intersect2]
)) THEN cast(0 as bit) END AS [C1]
FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]
Set
去掉重复项
myContext context = new myContext();
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string esql = "set(select value it.ItemID from myContext.DBItemList as it)";
ObjectQuery<string> query = context.CreateQuery<string>(esql);
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foreach (string r in query)
{
Console.WriteLine(r);
}
//去掉了重复项
SELECT
[Distinct1].[ItemID] AS [ItemID]
FROM ( SELECT DISTINCT
????[Extent1].[ItemID] AS [ItemID]
????FROM [dbo].[DBItemList] AS [Extent1]
) AS [Distinct1]
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esql函数
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统计类
Avg
平均值
myContext context = new myContext();
string esql = "SELECT value AVG(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
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/* print:
3
*/
BigCount
个数(long)
myContext context = new myContext();
string esql = "SELECT value BigCount(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<long> query = context.CreateQuery<long>(esql);
foreach (long n in query)
{
Console.WriteLine(n);
}
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/* print:
15
*/
Count
个数(int)
myContext context = new myContext();
string esql = "SELECT value Count(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
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/* print:
15
*/
Max
最大值
myContext context = new myContext();
string esql = "SELECT value Max(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
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/* print:
6
*/
Min
最小值
myContext context = new myContext();
string esql = "SELECT value Min(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
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/* print:
1
*/
Sum
合计
myContext context = new myContext();
string esql = "SELECT value Sum(it.ItemValue) FROM myContext.DBItemList as it";
ObjectQuery<int> query = context.CreateQuery<int>(esql);
foreach (int n in query)
{
Console.WriteLine(n);
}
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/* print:
54
*/
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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["Min"]);
}
?
/* print:
ItemID:a,Max:6,Min:2
ItemID:b,Max:5,Min:1
ItemID:c,Min:2
*/
?
数学类
Abs
绝对值
Abs(-2)
Round
随机数
Round(748.58)
?
日期
CurrentDateTime()
?
CurrentDateTimeOffset()
?
CurrentUtcDateTime()
?
Day( expression )
Day(cast('03/12/1998' as DateTime)) --返回:12
GetTotalOffsetMinutes
--返回:
SQL Server 2008 only
Hour ( expression )
Hour(cast('22:35:5' as DateTime)) --返回:22
Minute( expression )
Minute(cast('22:35:5' as DateTime)) --返回:35
Month (expression)
Month(cast('03/12/1998' as DateTime)) --返回:3
Second( expression )
Second(cast('22:35:5' as DateTime)) --返回:5
Year( expression )
Year(cast('03/12/1998' as DateTime)) --返回:1998
?
?
字符
Concat ( string1,string2)
字符串连接
Concat('abc','xyz') --返回:abcxyz
IndexOf( string1,string2)
字符串位置查找
IndexOf('xyz','abcxyz') --返回:4
Length ( string )
字符串长度
Legth('abcxyz') --返回:6
Reverse ( string )
字符串反转
Reverse('abcd') --返回:dcba
ToLower( string )
大写转小写
ToLower('ABC') --返回:abc
ToUpper( string )
小写转大写
ToUpper('abc') --返回:ABC
Trim( string )
去两端空格
Trim(' abc ') --返回:abc
LTrim( string )
去左端空格
LTrim(' abc') --返回:abc
RTrim( string )
去右端空格
?
Left ( string,length)
左端截取
Left('abcxyz',3) --返回:abc
Right ( string,length)
右端截取
Right('abcxyz',3) --返回:xyz
Substring ( string,start,length)
两端截取
Substring('abcxyz',4,3) --返回:xyz
?
?
?
esql语句
?
查询语句
SELECT
myContext context = new myContext();
?
string esql = "SELECT it.ItemValue as a,it.NameID FROM [DBItemList] AS it";
?
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
?
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},r["a"],r["NameID"]);
}
SELECT
1 AS [C1],
[Extent1].[NameID] AS [NameID]
FROM [dbo].[DBItemList] AS [Extent1]
WHERE
myContext context = new myContext();
?
string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE (it.ItemValue=5 or it .ItemValue=5) and it.NameID='n01' ";
?
ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
?
foreach (DBItemList r in query)
{
Console.WriteLine("{0},
[Extent1].[ItemValue] AS [ItemValue]
FROM [dbo].[DBItemList] AS [Extent1]
WHERE (([Extent1].[ItemValue] = 5) OR ([Extent1].[ItemValue] = 5)) AND ([Extent1].[NameID] = 'n01')
GROUP BY
myContext context = new myContext();
?
string esql = "SELECT it.ItemID,Sum(it.ItemValue) as ValueSum FROM [DBItemList] AS it GROUP BY it.ItemID ";
?
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
?
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},r["ValueSum"]);
}
SELECT
1 AS [C1],
????SUM([Extent1].[ItemValue]) AS [A1]
????FROM [dbo].[DBItemList] AS [Extent1]
????GROUP BY [Extent1].[ItemID]
) AS [GroupBy1]
ORDER BY
myContext context = new myContext();
?
string esql = "SELECT VALUE it FROM [DBItemList] AS it ORDER BY it.ItemValue,it.ItemID desc ";
?
ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);
?
foreach (DBItemList r in query)
{
Console.WriteLine("{0}, [Extent1].[ItemID] DESC
HAVING
myContext context = new myContext();
?
string esql = "SELECT it.ItemID,Count(it.ItemValue) as ValueSum FROM DBItemList AS it GROUP BY it.ItemID HAVING SUM(it.ItemValue) > 5";
?
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
?
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},
[GroupBy1].[A2] AS [C2]
FROM ( SELECT
????[Extent1].[ItemID] AS [K1],
????SUM([Extent1].[ItemValue]) AS [A1],
????COUNT([Extent1].[ItemValue]) AS [A2]
????FROM [dbo].[DBItemList] AS [Extent1]
????GROUP BY [Extent1].[ItemID]
) AS [GroupBy1]
WHERE [GroupBy1].[A1] > 5
JOIN
Cross Joins
Inner Joins
Left Outer Joins
Right Outer Joins
Full Outer Joins
?
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},r["ItemValueRemarks"]);
}
/*
c,好
c,5,其他
c,3,好
b,6,其他
b,1,差
c,好
a,其他
a,好
*/
?
?
?
?
?
esql 类型
?
简单类型
Null
is Null
is not Null
myContext context = new myContext();
?
ObjectQuery<typeTest> query = context.typeTest.Where("it.b is not Null");
?
foreach (typeTest r in query)
{
Console.WriteLine("{0},r.值);
}
Boolean
True,False
myContext context = new myContext();
?
ObjectQuery<typeTest> query = context.typeTest.Where("it.e==True");
?
foreach (typeTest r in query)
{
Console.WriteLine("{0},r.值);
}
Integer
Float,Double
Decimal
123
123.456
23.34
myContext context = new myContext();
?
ObjectQuery<typeTest> query = context.typeTest.Where("it.c==123");
foreach (typeTest r in query)
{
Console.WriteLine("{0},r.值);
}
String
"abcd"
N"U字符"
'abcd'
myContext context = new myContext();
?
// ObjectQuery<typeTest> query = context.typeTest.Where("it.b==N'冬冬'");
ObjectQuery<typeTest> query = context.typeTest.Where("it.b==/"冬冬/" ");
// ObjectQuery<typeTest> query = context.typeTest.Where("it.b=='冬冬'");
foreach (typeTest r in query)
{
Console.WriteLine("{0},r.值);
}
DateTime
DATETIME'2007-11-11 22:22'
DATETIME'2007-11-11 01:01:00.0000000'
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},r.值);
}
Time
TIME'22:11'
TIME'01:02:03.1234567'
?
DateTimeOffset
DATETIMEOFFSET'2007-11-11 22:11 +02:00'
DATETIMEOFFSET'2007-11-11 01:01:00.0000000 -02:00'
?
Binary
Binary'00ffaabb'
X'ABCabc'
BINARY '0f0f0f0F0F0F0F0F0F0F'
X'' –空
?
Guid
Guid'0321AF86-0AA5-4a86-A086-1D789FA54AA3'
GUID '0321AF86-0AA5-4a86-A086-1D789FA54AA3'
myContext context = new myContext();
ObjectQuery<typeTest> query = context.typeTest.Where("it.a==Guid'0321af86-0aa5-4a86-a086-1d789fa54aa3'");
foreach (typeTest r in query)
{
Console.WriteLine("{0},r.值);
}
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,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},v["ItemValue"],v["NameID"]);
}
集合
MULTISET(1,4)
{1,4}
SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue IN {1,3}
?
myContext context = new myContext();
?
string esql = "{1,3} ";
?
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},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
using SqlServer;
myContext context = new myContext();
string esql = "using SqlServer;select it.ItemValue,LEN(it.NameID) as NameIDLEN from myContext.DBItemList as it";
?
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
?
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},r["NameIDLEN"]);
}
SqlServer.函数
myContext context = new myContext();
string esql = "select it.ItemValue,SqlServer.LEN(it.NameID) as NameIDLEN from myContext.DBItemList as it";
?
ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);
?
foreach (DbDataRecord r in query)
{
Console.WriteLine("{0},r["NameIDLEN"]);
}
SELECT
1 AS [C1],
LEN([Extent1].[NameID]) AS [C2]
FROM [dbo].[DBItemList] AS [Extent1]
?
?
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},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},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},r.NameID);
}
（编辑：李大同）
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