impala having子句

Impala中的Having子句允許您指定過濾哪些組結果顯示在最終結果中的條件。

一般來說，Having子句與group by子句一起使用; 它將條件放置在由GROUP BY子句創(chuàng)建的組上。

語法

以下是Havingclause的語法。

select * from table_name ORDER BY col_name [ASC|DESC] [NULLS FIRST|NULLS LAST]

例

假設我們在數(shù)據(jù)庫my_db中有一個名為customers的表，其內(nèi)容如下 -

[quickstart.cloudera:21000] > select * from customers; 
Query: select * from customers 
+----+----------+-----+-------------+--------+ 
| id | name     | age | address     | salary | 
+----+----------+-----+-------------+--------+ 
| 1  | Ramesh   | 32  | Ahmedabad   | 20000  |
| 2  | Khilan   | 25  | Delhi       | 15000  | 
| 3  | kaushik  | 23  | Kota        | 30000  | 
| 4  | Chaitali | 25  | Mumbai      | 35000  | 
| 5  | Hardik   | 27  | Bhopal      | 40000  | 
| 6  | Komal    | 22  | MP          | 32000  | 
| 7  | ram      | 25  | chennai     | 23000  | 
| 8  | rahim    | 22  | vizag       | 31000  | 
| 9  | robert   | 23  | banglore    | 28000  | 
+----+----------+-----+-----------+--------+ 
Fetched 9 row(s) in 0.51s

[quickstart.cloudera:21000] > select max(salary) from customers group by age having max(salary) > 20000;

此查詢最初按年齡對表進行分組，并選擇每個組的最大工資，并顯示大于20000的工資，如下所示。

20000 
+-------------+ 
| max(salary) |
+-------------+ 
| 30000       |
| 35000       | 
| 40000       | 
| 32000       | 
+-------------+ 
Fetched 4 row(s) in 1.30s