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LATERAL VIEW Clause |
LATERAL VIEW Clause |
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
|
The LATERAL VIEW
clause is used in conjunction with generator functions such as EXPLODE
, which will generate a virtual table containing one or more rows. LATERAL VIEW
will apply the rows to each original output row.
LATERAL VIEW [ OUTER ] generator_function ( expression [ , ... ] ) [ table_alias ] AS column_alias [ , ... ]
-
OUTER
If
OUTER
specified, returns null if an input array/map is empty or null. -
generator_function
Specifies a generator function (EXPLODE, INLINE, etc.).
-
table_alias
The alias for
generator_function
, which is optional. -
column_alias
Lists the column aliases of
generator_function
, which may be used in output rows. We may have multiple aliases ifgenerator_function
have multiple output columns.
CREATE TABLE person (id INT, name STRING, age INT, class INT, address STRING);
INSERT INTO person VALUES
(100, 'John', 30, 1, 'Street 1'),
(200, 'Mary', NULL, 1, 'Street 2'),
(300, 'Mike', 80, 3, 'Street 3'),
(400, 'Dan', 50, 4, 'Street 4');
SELECT * FROM person
LATERAL VIEW EXPLODE(ARRAY(30, 60)) tableName AS c_age
LATERAL VIEW EXPLODE(ARRAY(40, 80)) AS d_age;
+------+-------+-------+--------+-----------+--------+--------+
| id | name | age | class | address | c_age | d_age |
+------+-------+-------+--------+-----------+--------+--------+
| 100 | John | 30 | 1 | Street 1 | 30 | 40 |
| 100 | John | 30 | 1 | Street 1 | 30 | 80 |
| 100 | John | 30 | 1 | Street 1 | 60 | 40 |
| 100 | John | 30 | 1 | Street 1 | 60 | 80 |
| 200 | Mary | NULL | 1 | Street 2 | 30 | 40 |
| 200 | Mary | NULL | 1 | Street 2 | 30 | 80 |
| 200 | Mary | NULL | 1 | Street 2 | 60 | 40 |
| 200 | Mary | NULL | 1 | Street 2 | 60 | 80 |
| 300 | Mike | 80 | 3 | Street 3 | 30 | 40 |
| 300 | Mike | 80 | 3 | Street 3 | 30 | 80 |
| 300 | Mike | 80 | 3 | Street 3 | 60 | 40 |
| 300 | Mike | 80 | 3 | Street 3 | 60 | 80 |
| 400 | Dan | 50 | 4 | Street 4 | 30 | 40 |
| 400 | Dan | 50 | 4 | Street 4 | 30 | 80 |
| 400 | Dan | 50 | 4 | Street 4 | 60 | 40 |
| 400 | Dan | 50 | 4 | Street 4 | 60 | 80 |
+------+-------+-------+--------+-----------+--------+--------+
SELECT c_age, COUNT(1) FROM person
LATERAL VIEW EXPLODE(ARRAY(30, 60)) AS c_age
LATERAL VIEW EXPLODE(ARRAY(40, 80)) AS d_age
GROUP BY c_age;
+--------+-----------+
| c_age | count(1) |
+--------+-----------+
| 60 | 8 |
| 30 | 8 |
+--------+-----------+
SELECT * FROM person
LATERAL VIEW EXPLODE(ARRAY()) tableName AS c_age;
+-----+-------+------+--------+----------+--------+
| id | name | age | class | address | c_age |
+-----+-------+------+--------+----------+--------+
+-----+-------+------+--------+----------+--------+
SELECT * FROM person
LATERAL VIEW OUTER EXPLODE(ARRAY()) tableName AS c_age;
+------+-------+-------+--------+-----------+--------+
| id | name | age | class | address | c_age |
+------+-------+-------+--------+-----------+--------+
| 100 | John | 30 | 1 | Street 1 | NULL |
| 200 | Mary | NULL | 1 | Street 2 | NULL |
| 300 | Mike | 80 | 3 | Street 3 | NULL |
| 400 | Dan | 50 | 4 | Street 4 | NULL |
+------+-------+-------+--------+-----------+--------+