本章介绍如何在SELECT语句中使用ORDER BY子句。ORDER BY子句用于基于一列检索详细信息，并按升序或降序对结果集进行排序。
句法
下面给出的是ORDER BY子句的语法：
SELECT [ALL | DISTINCT] select_expr, select_expr, ...
FROM table_reference
[WHERE where_condition]
[GROUP BY col_list]
[HAVING having_condition]
[ORDER BY col_list]]
[LIMIT number];
例
让我们以SELECT ... ORDER BY子句为例。使用名称为Id，Name，Salary，Designation和Dept的字段假设如下所示的员工表。生成一个查询以使用部门名称按顺序检索员工详细信息。
+------+--------------+-------------+-------------------+--------+
| ID | Name | Salary | Designation | Dept |
+------+--------------+-------------+-------------------+--------+
|1201 | Gopal | 45000 | Technical manager | TP |
|1202 | Manisha | 45000 | Proofreader | PR |
|1203 | Masthanvali | 40000 | Technical writer | TP |
|1204 | Krian | 40000 | Hr Admin | HR |
|1205 | Kranthi | 30000 | Op Admin | Admin |
+------+--------------+-------------+-------------------+--------+
以下查询使用上述方案检索员工详细信息：
hive> SELECT Id, Name, Dept FROM employee ORDER BY DEPT;
成功执行查询后，您将看到以下响应：
+------+--------------+-------------+-------------------+--------+
| ID | Name | Salary | Designation | Dept |
+------+--------------+-------------+-------------------+--------+
|1205 | Kranthi | 30000 | Op Admin | Admin |
|1204 | Krian | 40000 | Hr Admin | HR |
|1202 | Manisha | 45000 | Proofreader | PR |
|1201 | Gopal | 45000 | Technical manager | TP |
|1203 | Masthanvali | 40000 | Technical writer | TP |
+------+--------------+-------------+-------------------+--------+
JDBC程序
这是用于给定示例应用Order By子句的JDBC程序。
import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;
public class HiveQLOrderBy {
private static String driverName = "org.apache.hadoop.hive.jdbc.HiveDriver";
public static void main(String[] args) throws SQLException {
// Register driver and create driver instance
Class.forName(driverName);
// get connection
Connection con = DriverManager.getConnection("jdbc:hive://localhost:10000/userdb", "", "");
// create statement
Statement stmt = con.createStatement();
// execute statement
Resultset res = stmt.executeQuery("SELECT * FROM employee ORDER BY DEPT;");
System.out.println(" ID \t Name \t Salary \t Designation \t Dept ");
while (res.next()) {
System.out.println(res.getInt(1) + " " + res.getString(2) + " " + res.getDouble(3) + " " + res.getString(4) + " " + res.getString(5));
}
con.close();
}
}
将程序保存在名为HiveQLOrderBy.java的文件中。使用以下命令来编译和执行该程序。
$ javac HiveQLOrderBy.java
$ java HiveQLOrderBy
输出：
ID Name Salary Designation Dept
1205 Kranthi 30000 Op Admin Admin
1204 Krian 40000 Hr Admin HR
1202 Manisha 45000 Proofreader PR
1201 Gopal 45000 Technical manager TP
1203 Masthanvali 40000 Technical writer TP
1204 Krian 40000 Hr Admin HR
