array_slice
description
Syntax
ARRAY<T> array_slice(ARRAY<T> arr, BIGINT off, BIGINT len)返回一个子数组，包含所有从指定位置开始的指定长度的元素，如果输入参数为NULL，则返回NULL
如果off是正数，则表示从左侧开始的偏移量
如果off是负数，则表示从右侧开始的偏移量
当指定的off不在数组的实际范围内，返回空数组
如果len是负数，则表示长度为0notice
仅支持向量化引擎中使用
example
mysql> set enable_vectorized_engine=true;
mysql> select k2, k2[2:2] from array_type_table_nullable;
+-----------------+-------------------------+
| k2 | array_slice(`k2`, 2, 2) |
+-----------------+-------------------------+
| [1, 2, 3] | [2, 3] |
| [1, NULL, 3] | [NULL, 3] |
| [2, 3] | [3] |
| NULL | NULL |
+-----------------+-------------------------+
mysql> select k2, array_slice(k2, 2, 2) from array_type_table_nullable;
+-----------------+-------------------------+
| k2 | array_slice(`k2`, 2, 2) |
+-----------------+-------------------------+
| [1, 2, 3] | [2, 3] |
| [1, NULL, 3] | [NULL, 3] |
| [2, 3] | [3] |
| NULL | NULL |
+-----------------+-------------------------+
mysql> select k2, k2[2:2] from array_type_table_nullable_varchar;
+----------------------------+-------------------------+
| k2 | array_slice(`k2`, 2, 2) |
+----------------------------+-------------------------+
| ['hello', 'world', 'c++'] | ['world', 'c++'] |
| ['a1', 'equals', 'b1'] | ['equals', 'b1'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
+----------------------------+-------------------------+
mysql> select k2, array_slice(k2, 2, 2) from array_type_table_nullable_varchar;
+----------------------------+-------------------------+
| k2 | array_slice(`k2`, 2, 2) |
+----------------------------+-------------------------+
| ['hello', 'world', 'c++'] | ['world', 'c++'] |
| ['a1', 'equals', 'b1'] | ['equals', 'b1'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
+----------------------------+-------------------------+当指定off为负数:
mysql> select k2, k2[-2:1] from array_type_table_nullable;
+-----------+--------------------------+
| k2 | array_slice(`k2`, -2, 1) |
+-----------+--------------------------+
| [1, 2, 3] | [2] |
| [1, 2, 3] | [2] |
| [2, 3] | [2] |
| [2, 3] | [2] |
+-----------+--------------------------+
mysql> select k2, array_slice(k2, -2, 1) from array_type_table_nullable;
+-----------+--------------------------+
| k2 | array_slice(`k2`, -2, 1) |
+-----------+--------------------------+
| [1, 2, 3] | [2] |
| [1, 2, 3] | [2] |
| [2, 3] | [2] |
| [2, 3] | [2] |
+-----------+--------------------------+
mysql> select k2, k2[-2:2] from array_type_table_nullable_varchar;
+----------------------------+--------------------------+
| k2 | array_slice(`k2`, -2, 2) |
+----------------------------+--------------------------+
| ['hello', 'world', 'c++'] | ['world', 'c++'] |
| ['a1', 'equals', 'b1'] | ['equals', 'b1'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
+----------------------------+--------------------------+
mysql> select k2, array_slice(k2, -2, 2) from array_type_table_nullable_varchar;
+----------------------------+--------------------------+
| k2 | array_slice(`k2`, -2, 2) |
+----------------------------+--------------------------+
| ['hello', 'world', 'c++'] | ['world', 'c++'] |
| ['a1', 'equals', 'b1'] | ['equals', 'b1'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
| ['hasnull', NULL, 'value'] | [NULL, 'value'] |
+----------------------------+--------------------------+mysql> select k2, array_slice(k2, 0) from array_type_table;
+-----------+-------------------------+
| k2 | array_slice(`k2`, 0) |
+-----------+-------------------------+
| [1, 2, 3] | [] |
+-----------+-------------------------+
mysql> select k2, array_slice(k2, -5) from array_type_table;
+-----------+----------------------+
| k2 | array_slice(`k2`, -5) |
+-----------+----------------------+
| [1, 2, 3] | [] |
+-----------+----------------------+keywords
ARRAY,SLICE,ARRAY_SLICE