类别：: 半结构化和结构化数据函数（映射）

MAP_CONTAINS_KEY¶

确定指定的 MAP 是否包含指定的键。

语法¶

MAP_CONTAINS_KEY( <key> , <map> )

实参¶

key: 要查找的键。
map: 要搜索的映射。

返回¶

如果指定的映射包含指定的键，则返回 TRUE。
如果指定的映射不包含指定的键，则返回 FALSE。

使用说明¶

键表达式的类型必须与映射的键的类型匹配。如果类型为 VARCHAR，则类型可以是不同的长度。
对于 NULL 输入，输出为 NULL。

示例¶

该函数搜索 k1 键，并在映射中找到该键：

SELECT MAP_CONTAINS_KEY(
  'k1',{'k1':'v1','k2':'v2','k3':'v3'}::MAP(VARCHAR,VARCHAR))
  AS contains_key;

+--------------+
| CONTAINS_KEY |
|--------------|
| True         |
+--------------+

该函数搜索 k1 键，但在映射中找不到该键：

SELECT MAP_CONTAINS_KEY(
  'k1',{'ka':'va','kb':'vb','kc':'vc'}::MAP(VARCHAR,VARCHAR))
  AS contains_key;

+--------------+
| CONTAINS_KEY |
|--------------|
| False        |
+--------------+

SELECT 语句传入的键使用的类型与映射中的键不同：

SELECT MAP_CONTAINS_KEY(
  'k1',{'1':'va','2':'vb','3':'vc'}::MAP(NUMBER,VARCHAR))
  AS contains_key;

001065 (22023): SQL compilation error:
Function MAP_CONTAINS_KEY cannot be used with arguments of types VARCHAR(2) and MAP(NUMBER(38,0), VARCHAR(134217728))

Create a temporary table that contains MAP values:

CREATE OR REPLACE TEMP TABLE demo_maps(
  id INTEGER,
  attrs MAP(VARCHAR, VARCHAR),
  defaults MAP(VARCHAR, VARCHAR),
  keep_keys ARRAY(VARCHAR),
  ins_key VARCHAR,
  ins_val VARCHAR,
  update_existing BOOLEAN,
  del_key1 VARCHAR,
  del_key2 VARCHAR);

INSERT INTO demo_maps SELECT
  1,
  {'color':'red','size':'M','brand':'Acme'}::MAP(VARCHAR, VARCHAR),
  {'currency':'USD','size':'L'}::MAP(VARCHAR, VARCHAR),
  ['color','brand']::ARRAY(VARCHAR),
  'material',
  'cotton',
  TRUE,
  'size',
  'brand';

INSERT INTO demo_maps SELECT
  2,
  {'color':'blue','brand':'ZenCo'}::MAP(VARCHAR, VARCHAR),
  {'currency':'EUR','size':'M','brand':'ZenCo'}::MAP(VARCHAR, VARCHAR),
  ['brand','currency']::ARRAY(VARCHAR),
  'brand',
  'ZC',
  FALSE,
  'currency',
  'material';

查询表以显示数据：

SELECT * FROM demo_maps;

+----+---------------------+----------------------+--------------+----------+---------+-----------------+----------+----------+
| ID | ATTRS               | DEFAULTS             | KEEP_KEYS    | INS_KEY  | INS_VAL | UPDATE_EXISTING | DEL_KEY1 | DEL_KEY2 |
|----+---------------------+----------------------+--------------+----------+---------+-----------------+----------+----------|
|  1 | {                   | {                    | [            | material | cotton  | True            | size     | brand    |
|    |   "brand": "Acme",  |   "currency": "USD", |   "color",   |          |         |                 |          |          |
|    |   "color": "red",   |   "size": "L"        |   "brand"    |          |         |                 |          |          |
|    |   "size": "M"       | }                    | ]            |          |         |                 |          |          |
|    | }                   |                      |              |          |         |                 |          |          |
|  2 | {                   | {                    | [            | brand    | ZC      | False           | currency | material |
|    |   "brand": "ZenCo", |   "brand": "ZenCo",  |   "brand",   |          |         |                 |          |          |
|    |   "color": "blue"   |   "currency": "EUR", |   "currency" |          |         |                 |          |          |
|    | }                   |   "size": "M"        | ]            |          |         |                 |          |          |
|    |                     | }                    |              |          |         |                 |          |          |
+----+---------------------+----------------------+--------------+----------+---------+-----------------+----------+----------+

Determine whether the map in the attrs column contains the key in the ins_key column:

SELECT id, MAP_CONTAINS_KEY(ins_key, attrs) AS has_key
  FROM demo_maps;

+----+---------+
| ID | HAS_KEY |
|----+---------|
|  1 | False   |
|  2 | True    |
+----+---------+

The output shows the following:

The map in the attrs column in row 1 doesn't contain the key (material) in the ins_key column.
The map in the attrs column in row 2 contains the key (brand) in the ins_key column.