ADO.NET Entity Framework学习笔记(5) esql 语法

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

 

esql的查询结果集 ObjectQuery

 

ObjectQuery<实体>

myContext context = new myContext();   string esql = "SELECT VALUE DBItemList FROM myContext.DBItemList";   // ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql, context);   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   foreach (DBItemList r in query) { Console.WriteLine(r.NameID); }

myContext context = new myContext();   string esql = "SELECT VALUE it FROM myContext.DBItemList as it";   // ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql, context);   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   foreach (DBItemList r in query) { Console.WriteLine(r.NameID); }

 

ObjectQuery<DbDataRecord>

myContext context = new myContext();   string esql = "SELECT it.NameID FROM myContext.DBItemList as it";   //ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esql, context); ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);   foreach (DbDataRecord r in query) { Console.WriteLine(r["NameID"].ToString()); }

 

ObjectQuery<简单类型>

myContext context = new myContext();   string esql = "SELECT value count(it.NameID) FROM myContext.DBItemList as it";   // ObjectQuery<int> query = new ObjectQuery<int>(esql, context);   ObjectQuery<int> query = context.CreateQuery<int>(esql); foreach (int n in query) { Console.WriteLine(n); }

myContext context = new myContext();   string esql = "SELECT value it.NameID FROM myContext.DBItemList as it";   // ObjectQuery<int> query = new ObjectQuery<int>(esql, context);   ObjectQuery<string> query = context.CreateQuery<string>(esql); foreach (string n in query) { Console.WriteLine(n); }

 

 

esql的使用

 

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。

 

myContext context = new myContext(); context.DBItemList.Name = "wxd";   ObjectQuery<DBItemList> list = context.DBItemList.Where("wxd.ItemValue=5");

myContext context = new myContext();   var sql = "SELECT VALUE DBItemList FROM myContext.DBItemList"; var query = new ObjectQuery<DBItemList>(sql, context); query.Name = "wxd";   ObjectQuery<DBItemList> list = query.Where("wxd.ItemValue=@v", new ObjectParameter("v", 5));

 

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); }   /* print: 3 */

string esql = "select value it.ItemID 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 = "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"]); }

 

 

查询参数的使用

myContext context = new myContext();   string esql = "SELECT VALUE it FROM myContext.DBItemList as it where it.ItemValue=@v1 or it.NameID=@v2";   ObjectParameter v1 = new ObjectParameter("v1", 3); ObjectParameter v2 = new ObjectParameter("v2", "n01"); ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql,v1,v2);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}",r.NameID,r.ItemValue); }

 

中文字段

使用[]将字段括起来

myContext context = new myContext();   ObjectQuery<typeTest> query = context.typeTest.Where("it.值 ==22.22"); System.Console.WriteLine(query.CommandText); 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); }

myContext context = new myContext();   ObjectQuery<typeTest> query = context.typeTest.Where("it.[值] ==22.22"); System.Console.WriteLine(query.CommandText); 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); }

 

 

得到esql与sql字串

 

myContext context = new myContext();   string esql = "SELECT VALUE it FROM myContext.DBItemList as it";   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   Console.WriteLine(query.CommandText);   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]

 

CommandText属性

得到esql字串

ToTraceString方法

得到sql字串

 

 

 

ObjectQuery的Linq方法

 

 

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')

 

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},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue); }

SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS [NameID], [Extent1].[ItemID] AS [ItemID], [Extent1].[ItemValue] AS [ItemValue] FROM [dbo].[DBItemList] AS [Extent1] ORDER BY [Extent1].[ItemValue] ASC, [Extent1].[ItemID] DESC

 

Select

射影 ObjectQuery<DbDataRecord> Select(string projection, params ObjectParameter[] parameters);

myContext context = new myContext();   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]

 

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]

 

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},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);   }

SELECT TOP (3) [c].[AutoId] AS [AutoId], [c].[NameID] AS [NameID], [c].[ItemID] AS [ItemID], [c].[ItemValue] AS [ItemValue] FROM [dbo].[DBItemList] AS [c]

 

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},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);   }

SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS [NameID], [Extent1].[ItemID] AS [ItemID], [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

 

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},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);   }

SELECT TOP (3) [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS [NameID], [Extent1].[ItemID] AS [ItemID], [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

 

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},{1}", r["ItemID"], r["ValueSum"]); } /* a,23 b,8 c,23 */

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

 

 

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();   var r = context.DBItem.Include("DBItemList"); foreach (var dbitem in r) { foreach (var dbitemlist in dbitem.DBItemList) { Console.WriteLine("{0},{1}", dbitemlist.NameID, dbitemlist.ItemValue); } }

效果与下例相同 myContext context = new myContext();   var r = context.DBItem; foreach (var dbitem in r) { dbitem.DBItemList.Load(); foreach (var dbitemlist in dbitem.DBItemList) { Console.WriteLine("{0},{1}", dbitemlist.NameID, dbitemlist.ItemValue); } }

 

 

esql注释,成员访问,分行

 

注释	--
成员访问	.
分行	;

 

 

esql运算符

 

算术运算符

加	+
减	-
乘	*
除	/
模	%
负	-

 

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 ''
	% : _ : [ ] : [^] :

 

逻辑运算符

与	AND &&
非	NOT !
或	OR ||

 

 

区间

BETWEEN 之间	BETWEEN n AND m NOT BETWEEN n AND m
	myContext context = new myContext();   string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue BETWEEN 2 and 4";   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
	myContext context = new myContext();   ObjectQuery<DBItemList> query = context.DBItemList.Where(" it.ItemValue not BETWEEN 2 and 4");   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
IN 在集合中	IN {v,v} NOT IN{v,v}
	myContext context = new myContext();   string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue IN {1,2,3}";   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
	myContext context = new myContext();   ObjectQuery<DBItemList> query = context.DBItemList.Where("it.ItemValue not IN {1,2,3}");   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
EXISTS 存在	EXISTS(select from) NOT EXISTS(select from)
	myContext context = new myContext();   string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE exists(Select VALUE it2 From DBItem as it2 Where it2.ItemID=it.ItemID )";   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
	myContext context = new myContext();   ObjectQuery<DBItemList> query = context.DBItemList.Where("exists(Select VALUE it2 From DBItem as it2 Where it2.ItemID=it.ItemID )");   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, 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();   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' )";   ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, 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();   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);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
INTERSECT （交集） 获取不同集合的相同项	myContext context = new myContext();   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);   foreach (DBItemList r in query) { Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue); }
ANYELEMENT 集合中的第一个	myContext context = new myContext();   string esql = "ANYELEMENT(select value it from myContext.DBItemList as it where it.ItemID == 'a') "; ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);   //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},{1}", r.ItemID, 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();   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);   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();   string esql = "set(select value it.ItemID from myContext.DBItemList as it)"; ObjectQuery<string> query = context.CreateQuery<string>(esql);   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]

 

 

 

 

esql函数

 

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); }   /* 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); }   /* 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); }   /* 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); }   /* 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); }   /* 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); }   /* print: 54 */

 

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

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},{1}", r["a"], r["NameID"]); }
	SELECT 1 AS [C1], [Extent1].[ItemValue] AS [ItemValue], [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},{1}", r.ItemID, r.ItemValue); }
	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')
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},{1}", r["ItemID"], r["ValueSum"]); }
	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]
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},{1}", r.ItemID, r.ItemValue); }
	SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS [NameID], [Extent1].[ItemID] AS [ItemID], [Extent1].[ItemValue] AS [ItemValue] FROM [dbo].[DBItemList] AS [Extent1] ORDER BY [Extent1].[ItemValue] ASC, [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},{1}", r["ItemID"], r["ValueSum"]); }
	SELECT 1 AS [C1], [GroupBy1].[K1] AS [ItemID], [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},{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

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},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,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},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,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},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,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},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,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},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,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},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,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 ,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

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},{1}",r["ItemValue"],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},{1}",r["ItemValue"],r["NameIDLEN"]); }
SELECT 1 AS [C1], [Extent1].[ItemValue] AS [ItemValue], 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},{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); }