MAP_KEYS Function

Overview

The MAP_KEYS function is used to extract all the key values from the input map type data and return them in the form of an array.

Syntax

MAP_KEYS(map)

Parameters

• map: The input map data type, where K is the key type and V is the value type.

Return Value

Returns an array containing all the key values, of type array<K>.

Example Usage

1. Extract keys from a simple key-value map:

SELECT MAP_KEYS(map("苹果", 2, "香蕉", 3, "橙子", 4));
-- Return result: ["苹果", "香蕉", "橙子"]

2. Extract key from nested map:

SELECT MAP_KEYS(map(map("a", 1, "b", 2), map("c", 3, "d", 4)));
-- Return result: [{"a":1,"b":2}]

3. Extract key from an empty map:

SELECT MAP_KEYS(map());
-- Return result: []

Notes

• If the input map is empty, the MAP_KEYS function will return an empty array.
• The MAP_KEYS function does not change the order of keys in the original map.