动态SQL到LINQ实体框架
本文关键字:实体 框架 LINQ SQL 动态 | 更新日期: 2023-09-27 18:09:41
我只掌握了LINQ的基本知识。我会说SQL和JDBC,负责将动态PL/SQL转换为LINQ实体框架。如何在LINQ查询中添加条件WHERE子句?下面是一个非常简化的示例(省略类型info):
Q1 := 'SELECT bDay = b.birthday
address = b.address
FROM (' ;
Q2 := 'SELECT folks.birthday, Address.address
FROM folks,
(SELECT state,
surname AS name
FROM Individuals, Addresses
WHERE Individuals.addrId = Address.id
AND Addresses.state = 'CA' ) find1
,(SELECT state,
surname AS name
FROM Individuals, Addresses
WHERE Individuals.addrId = Address.id
AND Addresses.state = 'NV' ) find2
AND find1.state(+) = folks.state';
IF input_parm = 'RED' THEN
condAddOn :=condAddOn || 'AND folks.vacationHouse IS NOT NULL';
END IF;
IF input_parm = 'BLUE' THEN
condAddOn :=condAddOn || 'AND folks.vacationHouse = 'Cabin';
END IF;
...
OPEN curs FOR Q1 || Q2 || condAddOn ')b';
试图找出c#/LINQ语法,这是我的尝试(自下而上):
var find1 = (from addr in Addresses
from indiv in Individuals
where indiv.addrId = addr.addrID
select new
{
indiv.state,
indiv.surname
});
var find1OuterJoin = (from person in folks
join f1 in find1 on person.addrId equals f1.addrID
from f1OutJn in temp.DefaultIfEmpty()
select new
{
f1OutJn.state,
f1OutJn.surname
});
var Q2 = (from person in folks
from addr in addresses
from f1 in find1OuterJoin
where person.addrId == addr.addrId
&& f1.state == folks.state
select new
{
person.birthday
,addr.address
});
var Q1 = (from q2 in Q1
select new
{bDay = b.birthday
,address = b.address
});
我不知道1)如果我正确地将Q1引入Q22)如何引入动态WHERE子句以等效的游标语句结束:
OPEN curs FOR Q1 || Q2 || condAddOn ')b';
添加:我可以使用函数或表达式来包含动态位吗?我看到了对Expression和Expandable()的引用,但不确定。添加:我尝试在LINQ查询
当使用带有link的where
方法时,您将返回一个IQueryable
对象。这不会立即执行语句,因此可以执行以下操作:
var results = from person in folks
join addr in addresses
where person.addrId == addr.addrId
select new {
person.birthday,
addr.address
};
if(predicate){
results = from r in results
where /* new condition here */
select r;
}
var resultSet = results.ToList().AsEnumerable();
对于其他链接操作符,特别是在使用lambda linq时,也可以使用AsQuerably
扩展方法。
包括但不限于:
var results = folks.join(address,
person => person.addrId,
addr => addr.addrId
(person, addr) => new {
person.birthday,
addr.address
}).AsQueryable();
if(predicate)
{
results = results.where(/*predicate for the where condition*/);
}
var resultSet = results.ToList().AsEnumerable();