我想让我的查询更好,但是无法找到一个资源,当查询被发送到数据库时.

DBContext db = new DBContext();
Order _order = (from o in db
                where o.OrderID == "qwerty-asdf-xcvb"
                select o).FirstOrDefault();
String _custName = _order.Customer.Name +" "+_order.Customer.Surname;

_custName的赋值是否需要向数据库发出任何请求？

我正在尝试使用RepositoryRestResource和实现一个rest apiRestTemplate

除了加载@DBRef 之外，一切都运行良好

考虑这个数据模型：

public class Order
{
   @Id
   String id;

   @DBRef
   Customer customer;

   ... other stuff
}

public class Customer
{
    @Id
    String id;

    String name;

    ...
}

以及以下存储库（客户的类似存储库）

@RepositoryRestResource(excerptProjection = OrderSummary.class)
public interface OrderRestRepository extends MongoRepositor<Order,String>{}

其余 api 返回以下 JSON：

{
  "id" : 4,
  **other stuff**,
  "_links" : {
    "self" : {
      "href" : "http://localhost:12345/api/orders/4"
    },
    "customer" : {
      "href" : "http://localhost:12345/api/orders/4/customer"
    }
  }
}

如果由 resttemplate 正确加载，将创建一个新的 Order 实例，其中 customer = null

是否可以在存储库端急切地解决客户并嵌入 …

我正在使用PDO.所以我有一个声明,准备一个查询来选择一堆记录.例:

   //select duplicates
   $stmt = $this->db->prepare('SELECT Name COUNT( * ) AS CNT
            FROM  `Test`
            GROUP BY Name
            HAVING CNT > 1');

   $stmt2 = $this->db->prepare('SELECT * FROM Test2 WHERE TName = ?');

请注意,我确实需要选择所有数据,而不是某些列.该表包含5k记录,有时甚至更多.我需要选择所有5k记录,对于每个记录,我需要执行另一个查询来选择其他内容.

   $arr = array();
   while ($row = $stmt->fetch(DB::FETCH_ASSOC)) {
       $stmt2->execute($row['Name']);
       $arr[] = $stmt2->fetchAll(DB::FETCH_ASSOC);
   }

我知道我可以使用连接但是对于我的情况连接将不起作用,因为我需要遍历数据并为每个stmt1行执行stmt2.

当我运行它需要10-15分钟,我不能允许,我需要它更快.谁能告诉我这是什么问题？5k记录似乎没有多少循环.

      STMT1 returns up to 5.5k records

我需要返回每个副本的数据:

I am trying to work with spring, mybatis and mysql with jdbc. The only small problem I have after some queries, it throws an exception. The DB says: Too many connections.

So what I am trying to do to prevent the too many connection issue is to set up a connection pool. I have tried dbcp and bonecp also but both have the same behaviour. When I reload my page it just keeps loading in the browser and after some …

我有两个模型 — Note和Pinboard — 在 Django 应用程序中具有多对多关系。这两个模型通过另一个模型（Pin）相关联，因此我可以存储有关这种关系的其他信息。

我想在for Pinboard 中显示相关的Note实例。那不是问题。但我想预取笔记并在表格中的字段上订购它们。DetailViewpositionthrough

from django.db import models


class Note(models.Model):

    title = models.CharField(max_lenght=200)

    content = models.TextField()


class Pinboard(models.Model):

    title = models.CharField(max_lenght=200)

    notes = models.ManyToManyField(
        Note, blank=True, related_name='pinboards', through='Pin'
    )


class Pin(models.Model):

    class Meta:
        ordering = ['position', ]
        get_latest_by = 'position'

    pinboard = models.ForeignKey(Pinboard, related_name='note_pins')

    note = models.ForeignKey(Note, related_name='pinboard_pins')

    position = …