POSEXPLODE

Description

The table function is used in conjunction with Lateral View and can support multiple Lateral Views. It only supports the new optimizer.

It expands an array column into multiple rows and adds a column indicating the position, returning a struct type. When the array is NULL or empty, posexplode_outer returns NULL. Both posexplode and posexplode_outer will return NULL elements within the array.

Syntax

posexplode(array)
posexplode_outer(array)

Example

    CREATE TABLE IF NOT EXISTS `table_test`(
                `id` INT NULL,
                `name` TEXT NULL,
                `score` array<string> NULL
              ) ENGINE=OLAP
        DUPLICATE KEY(`id`)
        COMMENT 'OLAP'
        DISTRIBUTED BY HASH(`id`) BUCKETS 1
        PROPERTIES ("replication_allocation" = "tag.location.default: 1");

mysql> insert into table_test values (0, "zhangsan", ["Chinese","Math","English"]),(1, "lisi", ["null"]),(2, "wangwu", ["88a","90b","96c"]),(3, "lisi2", [null]),(4, "amory", NULL);


mysql [test_query_qa]>select * from table_test order by id;
+------+----------+--------------------------------+
| id   | name     | score                          |
+------+----------+--------------------------------+
|    0 | zhangsan | ["Chinese", "Math", "English"] |
|    1 | lisi     | ["null"]                       |
|    2 | wangwu   | ["88a", "90b", "96c"]          |
|    3 | lisi2    | [null]                         |
|    4 | amory    | NULL                           |
+------+----------+--------------------------------+

mysql [test_query_qa]>select id,name,score, k,v from table_test lateral view posexplode(score) tmp as k,v order by id;
+------+----------+--------------------------------+------+---------+
| id   | name     | score                          | k    | v       |
+------+----------+--------------------------------+------+---------+
|    0 | zhangsan | ["Chinese", "Math", "English"] |    0 | Chinese |
|    0 | zhangsan | ["Chinese", "Math", "English"] |    1 | Math    |
|    0 | zhangsan | ["Chinese", "Math", "English"] |    2 | English |
|    1 | lisi     | ["null"]                       |    0 | null    |
|    2 | wangwu   | ["88a", "90b", "96c"]          |    0 | 88a     |
|    2 | wangwu   | ["88a", "90b", "96c"]          |    1 | 90b     |
|    2 | wangwu   | ["88a", "90b", "96c"]          |    2 | 96c     |
|    3 | lisi2    | [null]                         |    0 | NULL    |
+------+----------+--------------------------------+------+---------+

mysql [test_query_qa]>select id,name,score, k,v from table_test lateral view posexplode_outer(score) tmp as k,v order by id;
+------+----------+--------------------------------+------+---------+
| id   | name     | score                          | k    | v       |
+------+----------+--------------------------------+------+---------+
|    0 | zhangsan | ["Chinese", "Math", "English"] |    0 | Chinese |
|    0 | zhangsan | ["Chinese", "Math", "English"] |    1 | Math    |
|    0 | zhangsan | ["Chinese", "Math", "English"] |    2 | English |
|    1 | lisi     | ["null"]                       |    0 | null    |
|    2 | wangwu   | ["88a", "90b", "96c"]          |    0 | 88a     |
|    2 | wangwu   | ["88a", "90b", "96c"]          |    1 | 90b     |
|    2 | wangwu   | ["88a", "90b", "96c"]          |    2 | 96c     |
|    3 | lisi2    | [null]                         |    0 | NULL    |
|    4 | amory    | NULL                           | NULL | NULL    |
+------+----------+--------------------------------+------+---------+

Keywords

POSEXPLODE,POSEXPLODE_OUTER