Derby - Order By语句

ORDER BY子句用于按其使用关键字的顺序排列输出集的内容，ASC代表升序，DESC代表降序，如果您不提及其中任何一个，则默认情况下内容将按升序排列。

Order By - 语法

以下是ORDER BY子句的语法-

SELECT * FROM table_name ORDER BY column_name ASC|DESC.

Order By - 命令行示例

假设无涯教程在数据库中有一个名为Employees的表，其中包含以下记录-

链接：https://www.learnfk.comhttps://www.learnfk.com/derby/apache-derby-order-by-clause.html

来源：LearnFk无涯教程网

ID |NAME |SALARY |LOCATION
------------------------------------------------------------------------------
1 |Amit |30000 |Vijayawada
2 |Kalyan |40000 |Vishakhapatnam
3 |Renuka |50000 |Delhi
4 |Learnfk |15000 |Vijayawada
5 |Trupthi |45000 |Kochin
6 |Suchatra |33000 |Vijayawada
7 |Rahul |39000 |Lucknow 

以下查询根据Employee的名称以升序排列表的内容。

ij> SELECT * FROM Employees ORDER BY Name;

这将生成以下输出-

ID |NAME |SALARY |LOCATION
---------------------------------------------------------------
1 |Amit |30000 |Hyderabad
4 |Learnfk |15000 |Mumbai
2 |Kalyan |40000 |Vishakhapatnam 
7 |Rahul |39000 |Lucknow
3 |Renuka |50000 |Delhi
6 |Suchatra |33000 |Pune
5 |Trupthi |45000 |Kochin
7 rows selected

类似地，以下查询根据Employee的薪水以降序排列表的内容-

ij> SELECT * FROM Employees ORDER BY Salary DESC;

这将生成以下输出-

ID |NAME |SALARY |LOCATION
---------------------------------------------------------------
3 |Renuka |50000 |Delhi
5 |Trupthi |45000 |Kochin
2 |Kalyan |40000 |Vishakhapatnam
7 |Rahul |39000 |Lucknow
6 |Suchatra |33000 |Pune
1 |Amit |30000 |Hyderabad
4 |Learnfk |15000 |Mumbai
7 rows selected

Order By - JDBC示例

本节教您如何使用JDBC在Derby中对表的内容进行排序，您可以使用ORDER BY子句和关键字ASC(表示升序)和DSC(表示降序)来按顺序排列记录。

无涯教程网

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class SortData {
   public static void main(String args[]) throws SQLException, ClassNotFoundException {
      //注册驱动
      Class.forName("org.apache.derby.jdbc.EmbeddedDriver");

      //创建连接
      String URL="jdbc:derby:SampleDB;create=true";
      Connection conn=DriverManager.getConnection(URL);

      //获取Statement对象
      Statement stmt=conn.createStatement();

      //创建表结构,插入一些测试数据
      String query="CREATE TABLE Employees("
         + "Id INT NOT NULL GENERATED ALWAYS AS IDENTITY, "
         + "Name VARCHAR(255), Salary INT NOT NULL, "
         + "Location VARCHAR(255), "
         + "PRIMARY KEY (Id))";
      String query="INSERT INTO Employees("
         + "Name, Salary, Location) VALUES "
         + "('Amit', 30000, 'Hyderabad'), "
         + "('Kalyan', 40000, 'Vishakhapatnam'), "
         + "('Renuka', 50000, 'Delhi'), "
         + "('Learnfk', 15000, 'Mumbai'), "
         + "('Trupthi', 45000, 'Kochin'), "
         + "('Suchatra', 33000, 'Pune'), "
         + "('Rahul', 39000, 'Lucknow'), "
         + "('Trupti', 45000, 'Kochin')";
      //执行SQL语句
      String query="SELECT Location, SUM(Salary) " + "from Employees GROUP BY Location";
      ResultSet rs=stmt.executeQuery(query);
      while(rs.next()) {
         System.out.println("Salary: "+rs.getString(1));
         System.out.println("Location: "+rs.getString(2));
         System.out.println(" ");
      }
   }
}

在执行上述程序时，您将获得以下输出-

Salary: Chennai
Location: 43000

Salary: Delhi
Location: 50000

Salary: Hyderabad
Location: 30000

Salary: Kochin
Location: 45000

Salary: Lucknow
Location: 39000

Salary: Mumbai
Location: 15000

Salary: Pune
Location: 33000