如何组合来自多个表的数据？（How to combine data from more than one tables?）

问题描述 (Problem Description)

如何提交查询？

解决方案 (Solution)

以下示例使用connection.commit（）方法执行查询。

import java.sql.*;
public class jdbcConn {
   public static void main(String[] args) throws Exception {
      Class.forName("org.apache.derby.jdbc.ClientDriver");
      Connection con = DriverManager.getConnection (
         "jdbc:derby://localhost:1527/testDb","name","pass");
      Statement stmt = con.createStatement();
      String query = "insert into emp values(2,'name1','job')";
      String query1 ="insert into emp values(5,'name2','job')";
      String query2 = "select * from emp";
      ResultSet rs = stmt.executeQuery(query2);
      int no_of_rows = 0;
      while (rs.next()) {
         no_of_rows++;
      }
      System.out.println("No. of rows before commit statement = "+ no_of_rows);
      con.setAutoCommit(false);
      stmt.execute(query1);
      stmt.execute(query);
      con.commit();
      rs = stmt.executeQuery(query2);
      no_of_rows = 0;
      while (rs.next()) {
         no_of_rows++;
      }
      System.out.println("No. of rows after commit statement = "+ no_of_rows);
      con.close();
   }
}      

结果 (Result)

上面的代码示例将产生以下结果。 结果可能会有所不同。

No. of rows before commit statement = 1
No. of rows after commit statement = 3