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-
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。
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");
</span><span class="com">//创建连接</span><span class="pln">
</span><span class="typ">String</span><span class="pln"> URL</span><span class="pun">=</span><span class="str">"jdbc:derby:SampleDB;create=true"</span><span class="pun">;</span><span class="pln">
</span><span class="typ">Connection</span><span class="pln"> conn</span><span class="pun">=</span><span class="typ">DriverManager</span><span class="pun">.</span><span class="pln">getConnection</span><span class="pun">(</span><span class="pln">URL</span><span class="pun">);</span><span class="pln">
</span><span class="com">//获取Statement对象</span><span class="pln">
</span><span class="typ">Statement</span><span class="pln"> stmt</span><span class="pun">=</span><span class="pln">conn</span><span class="pun">.</span><span class="pln">createStatement</span><span class="pun">();</span><span class="pln">
</span><span class="com">//创建表结构,插入一些测试数据</span><span class="pln">
</span><span class="typ">String</span><span class="pln"> query</span><span class="pun">=</span><span class="str">"CREATE TABLE Employees("</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"Id INT NOT NULL GENERATED ALWAYS AS IDENTITY, "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"Name VARCHAR(255), Salary INT NOT NULL, "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"Location VARCHAR(255), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"PRIMARY KEY (Id))"</span><span class="pun">;</span><span class="pln">
</span><span class="typ">String</span><span class="pln"> query</span><span class="pun">=</span><span class="str">"INSERT INTO Employees("</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"Name, Salary, Location) VALUES "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Amit, 30000, Hyderabad), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Kalyan, 40000, Vishakhapatnam), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Renuka, 50000, Delhi), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Learnfk, 15000, Mumbai), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Trupthi, 45000, Kochin), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Suchatra, 33000, Pune), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Rahul, 39000, Lucknow), "</span><span class="pln">
</span><span class="pun">+</span><span class="pln"> </span><span class="str">"(Trupti, 45000, Kochin)"</span><span class="pun">;</span><span class="pln">
</span><span class="com">//执行SQL语句</span><span class="pln">
</span><span class="typ">String</span><span class="pln"> query</span><span class="pun">=</span><span class="str">"SELECT Location, SUM(Salary) "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> </span><span class="str">"from Employees GROUP BY Location"</span><span class="pun">;</span><span class="pln">
</span><span class="typ">ResultSet</span><span class="pln"> rs</span><span class="pun">=</span><span class="pln">stmt</span><span class="pun">.</span><span class="pln">executeQuery</span><span class="pun">(</span><span class="pln">query</span><span class="pun">);</span><span class="pln">
</span><span class="kwd">while</span><span class="pun">(</span><span class="pln">rs</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">())</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"Salary: "</span><span class="pun">+</span><span class="pln">rs</span><span class="pun">.</span><span class="pln">getString</span><span class="pun">(</span><span class="lit">1</span><span class="pun">));</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"Location: "</span><span class="pun">+</span><span class="pln">rs</span><span class="pun">.</span><span class="pln">getString</span><span class="pun">(</span><span class="lit">2</span><span class="pun">));</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">" "</span><span class="pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
}
}
在执行上述程序时，您将获得以下输出-
Salary: Chennai Location: 43000Salary: Delhi Location: 50000
Salary: Hyderabad Location: 30000
Salary: Kochin Location: 45000
Salary: Lucknow Location: 39000
Salary: Mumbai Location: 15000
Salary: Pune Location: 33000
