LATERAL VIEW Clause

Description

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.

Syntax

  1. LATERAL VIEW [ OUTER ] generator_function ( expression [ , ... ] ) [ table_alias ] AS column_alias [ , ... ]

Parameters

  • 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 if generator_function have multiple output columns.

Examples

  1. CREATE TABLE person (id INT, name STRING, age INT, class INT, address STRING);
  2. INSERT INTO person VALUES
  3.     (100, 'John', 30, 1, 'Street 1'),
  4.     (200, 'Mary', NULL, 1, 'Street 2'),
  5.     (300, 'Mike', 80, 3, 'Street 3'),
  6.     (400, 'Dan', 50, 4, 'Street 4');
  8. SELECT * FROM person
  9.     LATERAL VIEW EXPLODE(ARRAY(30, 60)) tableName AS c_age
  10.     LATERAL VIEW EXPLODE(ARRAY(40, 80)) AS d_age;
  11. +------+-------+-------+--------+-----------+--------+--------+
  12. |  id  | name  |  age  | class  |  address  | c_age  | d_age  |
  13. +------+-------+-------+--------+-----------+--------+--------+
  14. | 100  | John  | 30    | 1      | Street 1  | 30     | 40     |
  15. | 100  | John  | 30    | 1      | Street 1  | 30     | 80     |
  16. | 100  | John  | 30    | 1      | Street 1  | 60     | 40     |
  17. | 100  | John  | 30    | 1      | Street 1  | 60     | 80     |
  18. | 200  | Mary  | NULL  | 1      | Street 2  | 30     | 40     |
  19. | 200  | Mary  | NULL  | 1      | Street 2  | 30     | 80     |
  20. | 200  | Mary  | NULL  | 1      | Street 2  | 60     | 40     |
  21. | 200  | Mary  | NULL  | 1      | Street 2  | 60     | 80     |
  22. | 300  | Mike  | 80    | 3      | Street 3  | 30     | 40     |
  23. | 300  | Mike  | 80    | 3      | Street 3  | 30     | 80     |
  24. | 300  | Mike  | 80    | 3      | Street 3  | 60     | 40     |
  25. | 300  | Mike  | 80    | 3      | Street 3  | 60     | 80     |
  26. | 400  | Dan   | 50    | 4      | Street 4  | 30     | 40     |
  27. | 400  | Dan   | 50    | 4      | Street 4  | 30     | 80     |
  28. | 400  | Dan   | 50    | 4      | Street 4  | 60     | 40     |
  29. | 400  | Dan   | 50    | 4      | Street 4  | 60     | 80     |
  30. +------+-------+-------+--------+-----------+--------+--------+
  32. SELECT c_age, COUNT(1) FROM person
  33.     LATERAL VIEW EXPLODE(ARRAY(30, 60)) AS c_age
  34.     LATERAL VIEW EXPLODE(ARRAY(40, 80)) AS d_age 
  35. GROUP BY c_age;
  36. +--------+-----------+
  37. | c_age  | count(1)  |
  38. +--------+-----------+
  39. | 60     | 8         |
  40. | 30     | 8         |
  41. +--------+-----------+
  43. SELECT * FROM person
  44.     LATERAL VIEW EXPLODE(ARRAY()) tableName AS c_age;
  45. +-----+-------+------+--------+----------+--------+
  46. | id  | name  | age  | class  | address  | c_age  |
  47. +-----+-------+------+--------+----------+--------+
  48. +-----+-------+------+--------+----------+--------+
  50. SELECT * FROM person
  51.     LATERAL VIEW OUTER EXPLODE(ARRAY()) tableName AS c_age;
  52. +------+-------+-------+--------+-----------+--------+
  53. |  id  | name  |  age  | class  |  address  | c_age  |
  54. +------+-------+-------+--------+-----------+--------+
  55. | 100  | John  | 30    | 1      | Street 1  | NULL   |
  56. | 200  | Mary  | NULL  | 1      | Street 2  | NULL   |
  57. | 300  | Mike  | 80    | 3      | Street 3  | NULL   |
  58. | 400  | Dan   | 50    | 4      | Street 4  | NULL   |
  59. +------+-------+-------+--------+-----------+--------+