MULTIMAP_FROM_ENTRIES
multimap_from_entries(array)
Description
Creates a multimap (a map where a single key can correspond to multiple values) from an array. The array format follows that of the map_entries function.
Unlike map_from_entries, when duplicate keys exist, multimap_from_entries aggregates all corresponding values into an array instead of throwing an error or overwriting.
Parameters
- array:
array<struct<key:K, value:V>>
Returns
map<K, array<V>>
Examples
select multimap_from_entries(array(struct(1, 'a'), struct(2, 'b'), struct(1, 'c')));
-- Result: {1:["a","c"],2:["b"]}
select multimap_from_entries(array(struct(1, 'a'), struct(2, 'b'), struct(3, 'c')));
-- Result: {1:["a"],2:["b"],3:["c"]}
select multimap_from_entries(array(struct(1, 'a'), struct(1, 'b'), struct(1, 'c')));
-- Result: {1:["a","b","c"]}
select multimap_from_entries(array(struct('a', 1), struct('a', 2), struct('b', 3)));
-- Result: {"a":[1,2],"b":[3]}
select multimap_from_entries(array(struct(1, 'a'), struct(2, null), struct(1, 'b')));
-- Result: {1:["a","b"],2:[null]}
select multimap_from_entries(array(struct('x', 1), struct('y', 2), struct('x', 3)));
-- Result: {"x":[1,3],"y":[2]}
Notes
- Keys cannot be null, otherwise an exception will be thrown
- Values can be null
- Preserves the first-appearance order of keys
