特殊函数(Special Functions)
展开函数(Expansion Functions)
unnest
将数组或映射展开为行。
参数
- array: 要展开的数组表达式。 可以是常量、列或函数,以及任意数组运算符的组合。
示例
> select unnest(make_array(1, 2, 3, 4, 5)) as unnested;
+----------+
| unnested |
+----------+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
+----------+
> select unnest(range(0, 10)) as unnested_range;
+----------------+
| unnested_range |
+----------------+
| 0 |
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
+----------------+
unnest (struct)
将 struct 的字段展开为独立的列。
参数
- struct: 要展开的对象表达式。 可以是常量、列或函数,以及任意对象运算符的组合。
示例
> create table foo as values ({a: 5, b: 'a string'}), ({a:6, b: 'another string'});
> create view foov as select column1 as struct_column from foo;
> select * from foov;
+---------------------------+
| struct_column |
+---------------------------+
| {a: 5, b: a string} |
| {a: 6, b: another string} |
+---------------------------+
> select unnest(struct_column) from foov;
+------------------------------------------+------------------------------------------+
| unnest_placeholder(foov.struct_column).a | unnest_placeholder(foov.struct_column).b |
+------------------------------------------+------------------------------------------+
| 5 | a string |
| 6 | another string |
+------------------------------------------+------------------------------------------+