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我想要實現的是：我在多個數據庫中有救護車數據。救護車的GPS在一個數據庫中跟蹤，在另一個數據庫中發送記錄，在另一個數據庫中發送醫療記錄。他們都有共同的一個獨特的關鍵導致火災/ EMS的事件。在這種情況下，我想使用JDBC來使用參數查詢兩個數據庫。我的參數是緊急事件的唯一ID。我想根據該唯一ID完成來自多個數據庫源的事件的完整報告。正如你從我下面顯示的代碼中可以看到的，我傳遞了兩次參數 - 一次在每個try catch塊（preStatement.setString（1，「MLC140701045015」）;）中。jdbc和使用單個參數查詢多個數據庫
我的目標是擁有一個下拉列表中的gui。用戶選擇一個事件並生成報告。該參數只能從gui的下拉列表中傳遞一次。
我的問題是：該參數只能傳遞一次嗎？ 我擁有文科學位，而不是計算機科學學位。你對我來說不能太簡單。請在你的回覆中明確表示。
package javaDatabase;
import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.PreparedStatement;
public class PreparedStatements
{
public static void main(String[] args)
{
// obtain information from dispatch
Connection conn = null;
Statement stmt = null;
try
{
conn = DriverManager
.getConnection
("jdbc:sqlserver://999.99.99.99;database=Incidents;integratedsecurity=false;user=myUser;password=myPassw
ord");
PreparedStatement preStatement = conn
.prepareStatement("SELECT I_EventNumber, I_Address,
I_tTimeDispatch FROM IIncident WHERE I_EventNumber = ?");
// pass a parameter
preStatement.setString(1, "MLC140701045015");
ResultSet rset = preStatement.executeQuery();
// output the results of the dispatch
while (rset.next())
{
String IncidentID = rset.getString("I_EventNumber");
String Address = rset.getString("I_Address");
String dtmIncident = rset.getString("I_tTimeDispatch");
System.out.println(IncidentID + ", " + Address + ", "
+ dtmIncident);
}
// clean up the program and close the connections
} catch (SQLException ex)
{
ex.printStackTrace();
} finally
{
try
{
if (stmt != null)
stmt.close();
if (conn != null)
conn.close();
} catch (SQLException ex)
{
ex.printStackTrace();
}
}
// obtain information from gps database.
Connection avlconn = null;
Statement avlstmt = null;
try
{
avlconn = DriverManager
.getConnection
("jdbc:sqlserver://777.77.77.77;database=gps_tracks;integratedsecurity=false;user=myUser;password=myPass
");
PreparedStatement preStatement = avlconn
.prepareStatement("SELECT RTRIM(AssignedIncident) AS [Mission],
RTRIM(CallSign) AS [Ambulance], RTRIM(UnitStatus) AS [Disposition], DateTimeStamp, Longitude, Latitude
FROM HISTORY_201407 WHERE AssignedIncident = ?");
// pass the same parameter previously. Why must this be done twice?
preStatement.setString(1, "MLC140701045015");
// return a result of the gps tracks
ResultSet rset = preStatement.executeQuery();
while (rset.next())
{
String mission = rset.getString("Mission");
String truck = rset.getString("Ambulance");
String disposition = rset.getString("Disposition");
Date dateTime = rset.getDate("DateTimeStamp");
Double longitude = rset.getDouble("Longitude");
Double latitude = rset.getDouble("Latitude");
System.out.println(mission + ", " + truck + ", " + disposition
+ ", " + dateTime + ", " + longitude + ", " + latitude);
}
// clean up the program and close out the connections
} catch (SQLException ex)
{
ex.printStackTrace();
} finally
{
try
{
if (avlstmt != null)
avlstmt.close();
if (avlconn != null)
avlconn.close();
} catch (SQLException ex)
{
ex.printStackTrace();
}
}
}
}