| --- | |
| { | |
| "title": "EXPLODE_MAP", | |
| "language": "en", | |
| "description": "The explodemap table function accepts a map type and expands the map into multiple rows, each containing a key-value pair." | |
| } | |
| --- | |
| ## Description | |
| The `explode_map` table function accepts a map type and expands the map into multiple rows, each containing a key-value pair. | |
| It should be used together with [`LATERAL VIEW`](../../../query-data/lateral-view.md). | |
| ## Syntax | |
| ```sql | |
| EXPLODE_MAP(<map>) | |
| ``` | |
| ## Parameters | |
| - `<map>` MAP type. | |
| ## Return Value | |
| - Returns a single-column, multi-row result composed of all elements in `<map>`. The column type is `Nullable<Struct<K, V>>`. | |
| - If `<map>` is NULL or empty, 0 rows are returned. | |
| ## Examples | |
| 0. Prepare data | |
| ```sql | |
| create table example( | |
| k1 int | |
| ) properties( | |
| "replication_num" = "1" | |
| ); | |
| insert into example values(1); | |
| ``` | |
| 1. Regular parameters | |
| ```sql | |
| select * from example lateral view explode_map(map("k", "v", "k2", 123, null, null)) t2 as c; | |
| ``` | |
| ```text | |
| +------+-----------------------------+ | |
| | k1 | c | | |
| +------+-----------------------------+ | |
| | 1 | {"col1":"k", "col2":"v"} | | |
| | 1 | {"col1":"k2", "col2":"123"} | | |
| | 1 | {"col1":null, "col2":null} | | |
| +------+-----------------------------+ | |
| ``` | |
| 2. Expand key-value pairs into separate columns | |
| ```sql | |
| select * from example lateral view explode_map(map("k", "v", "k2", 123, null, null)) t2 as k, v; | |
| ``` | |
| ```text | |
| +------+------+------+ | |
| | k1 | k | v | | |
| +------+------+------+ | |
| | 1 | k | v | | |
| | 1 | k2 | 123 | | |
| | 1 | NULL | NULL | | |
| +------+------+------+ | |
| ``` | |
| 3. Empty object | |
| ```sql | |
| select * from example lateral view explode_map(map()) t2 as c; | |
| ``` | |
| ```text | |
| Empty set (0.03 sec) | |
| ``` | |
| 4. NULL parameter | |
| ```sql | |
| select * from example lateral view explode_map(NULL) t2 as c; | |
| ``` | |
| ```text | |
| Empty set (0.03 sec) | |
| ``` |