### STACK

#### Description

The `STACK` function is a powerful data transformation tool that can stack multiple expressions into specified rows, generating new rows and columns. This function allows for flexible integration of different types of data during processing and can be used in conjunction with `LATERAL VIEW` to achieve more complex data operations.

#### Syntax
```sql
STACK(n, expr1, expr2, ..., exprK)
```
#### Parameter Description

* `n`: Integer, representing the number of rows to generate.
* `expr1 ~ exprK`: A list of expressions that are of the same type or can be implicitly converted to the same type.

#### Return Result

Returns a value of the same type as `expr1 ~ exprK`.

#### Usage Example

**Example 1: Basic Usage**
```sql
SELECT 'hello', STACK(2, 1, 2, 3) AS (first, second), 'world';
+---------+-------+--------+---------+
| 'hello' | first | second | 'world' |
+---------+-------+--------+---------+
| hello   | 1     | 2      | world   |
| hello   | 3     | null   | world   |
+---------+-------+--------+---------+
```
**Example 2: Using with** `` **
```sql
SELECT w, x, y FROM VALUES
  ('apple', 1, 2, 3, 4),
  ('banana', 11, 22, 33, 44),
  ('orange', 111, 222, 333, 444),
  ('dog', 1111, 2222, 3333, 4444) AS t(w, a, b, c, d)
LATERAL VIEW STACK(2, a, b, c) lv AS x, y;
+--------+------+------+
|   w    |  x   |  y   |
+--------+------+------+
| apple  | 1    | 2    |
| apple  | 3    | null |
| banana | 11   | 22   |
| banana | 33   | null |
| orange | 111  | 222  |
| orange | 333  | null |
| dog    | 1111 | 2222 |
| dog    | 3333 | null |
+--------+------+------+
```
**Example 3: Implicit Type Conversion**
```sql
SELECT STACK(2, 1, '2', 3) AS (col1, col2);
+------+------+
| col1 | col2 |
+------+------+
| 1    | 2    |
| 3    |      |
+------+------+
```