explode
description
表函数，需配合 Lateral View 使用。
将 array 列展开成多行。当 array 为NULL或者为空时，explode_outer 返回NULL。
explode 和 explode_outer 均会返回 array 内部的NULL元素。
语法：
explode(expr)
explode_outer(expr)example
mysql> set enable_vectorized_engine = true
mysql> select e1 from (select 1 k1) as t lateral view explode([1,2,3]) tmp1 as e1;
+------+
| e1 |
+------+
| 1 |
| 2 |
| 3 |
+------+
mysql> select e1 from (select 1 k1) as t lateral view explode_outer(null) tmp1 as e1;
+------+
| e1 |
+------+
| NULL |
+------+
mysql> select e1 from (select 1 k1) as t lateral view explode([]) tmp1 as e1;
Empty set (0.010 sec)
mysql> select e1 from (select 1 k1) as t lateral view explode([null,1,null]) tmp1 as e1;
+------+
| e1 |
+------+
| NULL |
| 1 |
| NULL |
+------+
mysql> select e1 from (select 1 k1) as t lateral view explode_outer([null,1,null]) tmp1 as e1;
+------+
| e1 |
+------+
| NULL |
| 1 |
| NULL |
+------+keywords
EXPLODE,EXPLODE_OUTER,ARRAY