查询 Java 不执行

Question

我正在尝试在我的 Java 程序中对 eclipse 执行查询，但它总是以异常退出并且不执行查询，我在这里阅读了很多帖子，但没有人可以帮助我.

public static ResultSet queryAccAmount;

public static String query = " SELECT COUNT(*) s FROM (SELECT  L.ACCNUMBER AS AN, L.PROD AS PRD " 
        + " FROM LTRANS(nolock) L, AN(nolock) ANM " 
        + " WHERE DATA BETWEEN 20210101 AND 20210228 " 
        + " AND L.PRD IN (1, 2, 3) " 
        + " AND L.ACCNUMBER = ANM.ACCNUMBER "
        + " AND L.ISS = ANM.ISS " 
        + " AND L.PROD = ANM.PROD " 
        + " AND L.MESSAGECODE <> 'MESSAGE' "
        + " GROUP BY L.PROD, L.ACCNUMBER) S; ";

public static void main(String[] args) throws InterruptedException {

        Connection c = connect();

        int accAmount = 0;
        
        try {
            queryAccAmount = c.createStatement().executeQuery(query);

            accAmount = Integer.parseInt(queryAccAmount.getString(1));
            LOG.info("Mounth total: " + accAmount);
        } catch (Exception ex) {
            System.out.println(ex);
        } finally {
            TimeUnit.SECONDS.sleep(10);
            disconnect();
        }
}

执行程序时的错误：

JavaError

但在基地有数据：

DataBase

我不知道这是什么问题，谁能帮助我我已经很感激了！

Answer 1

在你的尝试中尝试这样做：

try {queryAccAmount = c.createStatement().executeQuery(query);
        if(queryAccAmount.next){

        accAmount = Integer.parseInt(queryAccAmount.getString(1));}

        LOG.info("Mounth total: " + accAmount);
    } catch (Exception ex) {
        System.out.println(ex);
    } finally {
        TimeUnit.SECONDS.sleep(10);
        disconnect();
    }

Answer 2

您需要调用 executeQuery 一次，然后在循环中读取结果，例如用工作示例更新我的评论：-

import java.sql.*;

public class JDBCConnector {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost/EMP";

   //  Database credentials
   static final String USER = "root";
   static final String PASS = "mysql";
   
   public static void main(String[] args) {
   Connection conn = null;
   Statement stmt = null;
   try{
      //STEP 2: Register JDBC driver
      Class.forName("com.mysql.jdbc.Driver");

      //STEP 3: Open a connection
      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL,USER,PASS);

      //STEP 4: Execute a query
      System.out.println("Creating statement...");
      stmt = conn.createStatement();
      String sql;
      sql = "SELECT id, first, last, age FROM Employees";
      ResultSet rs = stmt.executeQuery(sql);

      //STEP 5: Extract data from result set
      while(rs.next()){
         //Retrieve by column name
         int id  = rs.getInt("id");
         int age = rs.getInt("age");
         String first = rs.getString("first");
         String last = rs.getString("last");

         //Display values
         System.out.print("ID: " + id);
         System.out.print(", Age: " + age);
         System.out.print(", First: " + first);
         System.out.println(", Last: " + last);
      }
      //STEP 6: Clean-up environment
      rs.close();
      stmt.close();
      conn.close();
   }catch(SQLException se){
      //Handle errors for JDBC
      se.printStackTrace();
   }catch(Exception e){
      //Handle errors for Class.forName
      e.printStackTrace();
   }finally{
      //finally block used to close resources
      try{
         if(stmt!=null)
            stmt.close();
      }catch(SQLException se2){
      }// nothing we can do
      try{
         if(conn!=null)
            conn.close();
      }catch(SQLException se){
         se.printStackTrace();
      }//end finally try
   }//end try
   System.out.println("Goodbye!");
}//end main
}//end FirstExample