小编Mic*_*uen的帖子

我有一张这样的桌子

childid      parentid
------------------------
1       0
2       1
3       2
4       2
5       3
6       4
7       0
8       7
9       8
10      1

如果我将childid设为5,那么parentid将为1(输出)

如果我将childid设为9,那么parentid将为7.(输出)

即根parentid为0,查询应该停在那里.

如何解决这样的查询？

请帮忙.

我需要一些帮助查询分层数据.这是单个简单的表,其中parent_id引用id,对于根条目可以为null.

  create table edition (
      id           NUMBER(20),
      parent_id    NUMBER(20)
  );

对于表中的每条记录,我需要找到具有最大id的最深的孩子.如果记录没有子节点,则应返回其自己的id.我自己尝试但是在使用START WITH A.id = B.idA和B是子查询的地方失败了,看起来Oracle不允许这样的连接.

以下是示例数据:

     id      parent_id
   ----------------------
      1        NULL
      2           1
      3           1
      4           1
      5           4
      6           5
      7           5

和样本结果

     id      result
   ----------------------
      1           7
      2           2
      3           3
      4           7
      5           7
      6           6
      7           7

我有一张这样的桌子

create table public.incominglog
(
    envelopeid        varchar(36) default ''::character varying not null,
    messagetype       text        default NULL::character varying,
    initialenvelopeid varchar(36) default NULL::character varying,
    processid         varchar(36) default NULL::character varying,
    logtimestamp      timestamp,
    customscode       varchar(8),
    exchtypeid        integer
);
create unique index incominglog_envelopeid_uindex
    on public.incominglog (envelopeid);
create unique index incominglog_initialenvelopeid_uindex
    on public.incominglog (initialenvelopeid);

我正在尝试插入这样的值

INSERT INTO
    incominglog (
        envelopeid,
        messagetype,
        initialenvelopeid,
        processid,
        logtimestamp,
        customscode,
        exchtypeid
    )
VALUES
    (
        'ae2a2b46-ae4f-42a1-ada3-1f8f0aff7361',
        'CMN.00001',
        'aad06a96-667f-42c9-9196-8e0fec103d8b',
        '4fed3854-e1de-42eb-b2c7-3ad714b58a9e',
        '2019-04-17 14:57:54.195588',
        '10210130',
        '19200'
    ) 
ON CONFLICT (initialenvelopeid) 
DO update set
    envelopeid = …

var insInvoice = new NpgsqlCommand(
    @"INSERT INTO invoice_detail(
    invoice_id,
    invoice_detail_id,
    product_id,
    qty,
    price,
    amount)
    VALUES (
    :_invoice_id,
    :_invoice_detail_id,
    :_product_id,
    :_qty,
    :_price,
    :_qty * :_price)", c);


with(var p = insInvoice.Parameters)
{
    p.Add("_invoice_id", NpgsqlDbType.Uuid, 0, "invoice_id");
    p.Add("_invoice_detail_id", NpgsqlDbType.Uuid, 0, "invoice_detail_id");
    p.Add("_product_id", NpgsqlDbType.Uuid, 0, "product_id");
    p.Add("_qty", NpgsqlDbType.Integer, 0, "qty");
    p.Add("_price", NpgsqlDbType.Numeric, 0, "price");
}

kludge:

for(var p = insInvoice.Parameters; false;)
{       
    p.Add("_invoice_id", NpgsqlDbType.Uuid, 0, "invoice_id");
    p.Add("_invoice_detail_id", NpgsqlDbType.Uuid, 0, "invoice_detail_id");
    p.Add("_product_id", NpgsqlDbType.Uuid, 0, "product_id");
    p.Add("_qty", NpgsqlDbType.Integer, 0, "qty");
    p.Add("_price", NpgsqlDbType.Numeric, 0, "price");      
}

试着这样做:

SELECT CASE WHEN field = true THEN one * another ELSE one END as case_field 
FROM table WHERE case_field >= 9000

并收到case_field不存在的错误.

是否可以在不重复CASE的情况下执行此操作？

我正在努力实现:

select StoreId, StoreName from Store where StoreId in (
     select StoreId from Employee where EmployeeName = 'Steve Jobs')

我有这个代码:

public class Store
{
  public virtual int StoreId { get; private set; }
  public virtual string StoreName { get; set; }

  public virtual IList<Employee> Staff { get; set; }
}

public class Employee
{
  public virtual Store Store { get; set; }

  public virtual int EmployeeId { get; private set; }
  public virtual string EmployeeName { get; set; }
} …

是否可以声明方法的返回类型,例如IList小于您在内部定义的方法,例如List？它会编译运行吗？

   protected static IList<String> GetJobFiles(String folder, String fileExtension)
    {
        List<String> jobFiles = new List<String>();

        if (System.IO.Directory.Exists(folder))
        {
            string[] files = Directory.GetFiles(folder, fileExtension);

            // Check if for matching files
            if (files.Length > 0)
            {
                // add the files to our list collection
                jobFiles.AddRange(files);
            }

        }

        return jobFiles;
    }

这个学期在大学我有一个名为Data Structures的课程,教授允许学生选择他们喜欢的语言.因为我想成为一名游戏程序员,而且我不能再使用Java了,所以我选择了C++ ......但是现在我因为缺乏这种语言的知识而陷入困境.我必须做以下事情:创建一个SuperArray,它就像一个Delphi数组(你可以选择它的起始和结束索引).我的代码如下:

main.cpp中

#include <iostream>
#include "SuperArray.h"    

using namespace std;

int main(int argc, char** argv) 
{
    int start, end;
    cout << "Starting index" << endl;
    cin >> start;
    cout << "Ending index:" << endl;
    cin >> end;
    SuperArray array = new SuperArray(start,end); 
}

superarray.h

#ifndef _SUPERARRAY_H
#define _SUPERARRAY_H

class SuperArray
{
public:
    SuperArray(int start, int end);
    void add(int index,int value);
    int get(int index);
    int getLength();
private:
    int start, end, length;
    int *array;

};

#endif  /* _SUPERARRAY_H */

superarray.cpp

#include …

如何转换这个NHibernate HQL(工程)......

static IList<Phone> PhoneList()
{
    ISession session = OpenSession();

    IQuery query = session.CreateQuery("from Phone p where p.Kontact.ContactName = :_contact_name");
    query.SetParameter("_contact_name", "lennon");

    IList<Phone> contacts = query.List<Phone>();

    return contacts;        
}

...到Linq-to-NHibernate(不工作):

static IList<Phone> PhoneListUsingLinq()
{
    string contactName = "lennon";

    ISession session = OpenSession();

    var contacts = from Phone p in session.Query<Phone>()
        where p.Kontact.ContactName == contactName
        select p;

    return contacts.ToList();

}

对象:

public class Contact
{
    public virtual int ContactId { get; set; }
    public virtual string ContactName { get; set; } …

如果使用带有子查询的select case语句将else语句改为单个查询,我需要更改以下过程...

 if((select COUNT(*) from pseb.dbo.meterattributedetails where meterid=@meterid)=0)
  select @emf=EMF from pseb.dbo.METERMASTER where MeterID=@meterid
  else  if((select COUNT(*) from pseb.dbo.meterattributedetails where meterid=@meterid and dateadd(day,1,@fromdate)<DateTime)>0) 
    select top 1 @emf=oldvalue from pseb.dbo.meterattributedetails  where MeterID=@meterid and dateadd(day,1,@fromdate)<datetime order by DateTime 
     else 
  select top 1 @emf=newvalue from pseb.dbo.meterattributedetails  where meterid=@meterid and DateTime<@fromdate order by DateTime desc

meterattribute表结构如下:

AttributeID AttributeName   Oldvalue    newvalue    DateTime    meterid
1           EMF         2.00000         4.00000        2012-07-05   4756
1           EMF         4.00000         6.00000        2012-07-10   4756
1           EMF         6.00000         8.00000        2012-07-15   4756
1           EMF         8.00000        10.00000 …