---
{
    "title": "Lateral View",
    "language": "zh-CN"
}
---

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# Lateral View

## description

Lateral view 语法可以搭配 Table Function，完成将一行数据扩展成多行（列转行）的需求。

语法：

```
...
FROM table_name
lateral_view_ref[ lateral_view_ref ...]

lateral_view_ref:

LATERAL VIEW table_function(...) view_alias as col_name
```
    
Lateral view 子句必须跟随在表名或子查询之后。可以包含多个 Lateral view 子句。`view_alias` 是对应 Lateral View 的名称。`col_name` 是表函数 `table_function` 产出的列名。

目前支持的表函数：

1. `explode_split`
2. `explode_bitmap`
3. `explode_json_array`

具体函数说明可参阅对应语法帮助文档。

table 中的数据会和各个 Lateral View 产生的结果集做笛卡尔积后返回上层。

## example

这里只给出 Lateral View 的语法示例，具体含义和产出的结果说明，可参阅对应表函数帮助文档。

1.

```
select k1, e1 from tbl1
lateral view explode_split(v1, ',') tmp1 as e1 where e1 = "abc";
```

2.

```
select k1, e1, e2 from tbl2
lateral view explode_split(v1, ',') tmp1 as e1
lateral view explode_bitmap(bitmap1) tmp2 as e2
where e2 > 3;
```

3.

```
select k1, e1, e2 from tbl3
lateral view explode_json_array_int("[1,2,3]") tmp1 as e1
lateral view explode_bitmap(bitmap_from_string("4,5,6")) tmp2 as e2;
```

4.

```
select k1, e1 from (select k1, bitmap_union(members) as x from tbl1 where k1=10000 group by k1)tmp1
lateral view explode_bitmap(x) tmp2 as e1;
```

## keyword

    LATERAL, VIEW