Question

我的数据库看起来像这样

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            SqlConnection conn = new SqlConnection("Server=********;Database=*********;Integrated Security=true");
            conn.Open();
            SqlCommand cmd = new SqlCommand("SELECT p.cFName, p.cLName, s.cSugTitle, s.cEcrno, g.cName, h.mNotes, u.UserID, u.NetworkID FROM people p INNER JOIN suggest s ON p.cidPeople = s.cidPeople_WhoEntered INNER JOIN Grp g on s.cidGrp = g.cidGrp INNER JOIN history h ON h.cidSuggest = s.cidSuggest INNER JOIN users u ON u.cidPeople = p.cidPeople", conn);
            SqlDataReader reader = cmd.ExecuteReader();

            String path = @"C:\Users\AEEVANS\Desktop\example.csv";

            using (StreamWriter sr = File.AppendText(path))
            {
                while (reader.Read())
                {
                    sr.WriteLine("{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}", reader.GetString(0), reader.GetString(1), reader.GetString(2), reader.GetString(3), reader.GetString(4), reader.IsDBNull(5) ? null : reader.GetString(5), reader.GetString(6), reader.IsDBNull(7) ? null : reader.GetString(7));
                    sr.Close();
                }
            }

            reader.Close();
            conn.Close();

            if (Debugger.IsAttached)
            {
                Console.ReadLine();
            }

        }
        }
    }

我正在尝试创建一个函数，该函数根据函数的输入参数选择行，并返回此行和下2行。

到目前为止，我所做的是该函数返回具有匹配参数的记录。

ID      SSID      BSSID         RSSI
1.      ABCD      ab:cd:17      -68 
2.      efgh      cd:as:25      -60
3.      ijkl      cs:gb:d6      -75 
4.      abcd      dc:5g:f4      -72 
....
518.    ABCD      ab:cd:17      -68
519.    asfd      ag:4g:32      -60
520.    aasd      gd:5g:56      -79

我要查找的结果是，例如，如果public Cursor getRequiredData(String mac, int level){ SQLiteDatabase db = this.getReadableDatabase(); Cursor res = db.rawQuery("SELECT BSSID, RSSI FROM Scans_table WHERE BSSID =? AND RSSI =?", new String[] {mac, String.valueOf(level)}); return res; }参数为mac和ab:cd:17，则该函数返回第1、2、3行（提供了示例数据）

编辑：

level = -68

此查询工作正常，但是它只给我第一条与Cursor res = db.rawQuery("SELECT * from Scans_table st where ID >= " + "( select ID from Scans_table where BSSID =? AND RSSI =? ) order by st.ID asc limit 3 ", new String[] {mac, String.valueOf(level)});和mac参数匹配的记录，以及接下来的两条具有最高String.valueOf(level)的记录。如果我的表有多个记录且这些参数的值相同怎么办？有没有办法获得所有匹配的记录和ID最高的2条下一条？（样本数据）

Answer 1

假设“下一行”是指“具有次高ID的行”，则可以使用子查询来获取所需行的ID，然后使用order by和limit来获取接下来的两行：

select st.*
from scans_table st
where st.id >= (select st2.id from scans_table st2 where <your conditions are here>)
order by st.id asc
limit 3;

SQLite查询选择一行并返回其下两行

1 个答案: