HiveQL Select語(yǔ)句與Order By子句

本章介紹了如何使用SELECT語(yǔ)句的ORDER BY子句。ORDER BY子句用于檢索基于一列的細(xì)節(jié)并設(shè)置排序結(jié)果按升序或降序排列。

語(yǔ)法

下面給出的是ORDER BY子句的語(yǔ)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];

示例

讓我們舉個(gè)SELECT ... ORDER BY子句的例子。假設(shè)員工表，如下Id, Name, Salary, Designation, 和 Dept 的字段，生成一個(gè)查詢用于檢索員工的詳細(xì)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  |
+------+--------------+-------------+-------------------+--------+

下面是使用上述業(yè)務(wù)情景查詢檢索員工詳細(xì)信息：

hive> SELECT Id, Name, Dept FROM employee ORDER BY DEPT;

成功執(zhí)行查詢后，能看到以下回應(yīng)：

+------+--------------+-------------+-------------------+--------+
| 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

下面是JDBC程序應(yīng)用給定Order By子句的例子。

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();
   }
}

保存程序在一個(gè)名為HiveQLOrderBy.java文件。使用下面的命令來(lái)編譯并執(zhí)行這個(gè)程序。

$ javac HiveQLOrderBy.java
$ java HiveQLOrderBy

輸出

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