HiveQL Select Order By

本章介紹瞭如何使用SELECT語句的ORDER BY子句。ORDER BY子句用於檢索基於一列的細節並設置排序結果按升序或降序排列。

語法

下面給出的是ORDER BY子句的語法：

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SELECT ... ORDER BY子句的例子。假設員工表，如下Id, Name, Salary, Designation, 和 Dept 的字段，生成一個查詢用於檢索員工的詳細信息。

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

下面是使用上述業務情景查詢檢索員工詳細信息：

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

成功執行查詢後，能看到以下回應：

+------+--------------+-------------+-------------------+--------+
| 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(); } }

保存程序在一個名爲HiveQLOrderBy.java文件。使用下面的命令來編譯並執行這個程序。

$ 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