列转行 (Lateral View)

与生成器函数（例如 EXPLODE）结合使用，将生成包含一个或多个行的虚拟表。 LATERAL VIEW 将行应用于每个原始输出行。

语法

LATERAL VIEW generator_function ( expression [, ...] ) table_identifier AS column_identifier [, ...]

参数

• generator_function

  生成器函数（EXPLODE、EXPLODE_SPLIT 等）。

• table_identifier

  generator_function 的别名。

• column_identifier

  列出列别名 generator_function，它可用于输出行。列标识符的数目必须与 generator 函数返回的列数匹配。

示例

CREATE TABLE `person` (
  `id` int(11) NULL,
  `name` text NULL,
  `age` int(11) NULL,
  `class` int(11) NULL,
  `address` text NULL
) ENGINE=OLAP
UNIQUE KEY(`id`)
COMMENT 'OLAP'
DISTRIBUTED BY HASH(`id`) BUCKETS 1
PROPERTIES (
"replication_allocation" = "tag.location.default: 1",
"in_memory" = "false",
"storage_format" = "V2",
"disable_auto_compaction" = "false"
);

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');

mysql> SELECT * FROM person
    ->     LATERAL VIEW EXPLODE(ARRAY(30, 60)) tableName AS c_age;
+------+------+------+-------+----------+-------+
| id   | name | age  | class | address  | c_age |
+------+------+------+-------+----------+-------+
|  100 | John |   30 |     1 | Street 1 |    30 |
|  100 | John |   30 |     1 | Street 1 |    60 |
|  200 | Mary | NULL |     1 | Street 2 |    30 |
|  200 | Mary | NULL |     1 | Street 2 |    60 |
|  300 | Mike |   80 |     3 | Street 3 |    30 |
|  300 | Mike |   80 |     3 | Street 3 |    60 |
|  400 | Dan  |   50 |     4 | Street 4 |    30 |
|  400 | Dan  |   50 |     4 | Street 4 |    60 |
+------+------+------+-------+----------+-------+
8 rows in set (0.12 sec)