15.18. Map Functions and Operators
Subscript Operator: []
The []
operator is used to retrieve the value corresponding to a given key from a map:
SELECT name_to_age_map['Bob'] AS bob_age;
Map Functions
-
cardinality
(x) → bigint Returns the cardinality (size) of the map
x
.
-
element_at
(map<K, V>, key) → V Returns value for given
key
, orNULL
if the key is not contained in the map.
-
map
() → map<unknown, unknown> Returns an empty map.
SELECT map(); -- {}
-
map
(array<K>, array<V>) → map<K,V> Returns a map created using the given key/value arrays.
SELECT map(ARRAY[1,3], ARRAY[2,4]); -- {1 -> 2, 3 -> 4}
See also
map_agg()
andmultimap_agg()
for creating a map as an aggregation.
-
map_concat
(x<K, V>, y<K, V>) → map<K,V> Returns the union of two maps. If a key is found in both
x
andy
, that key’s value in the resulting map comes fromy
.
-
map_filter
(map<K, V>, function) → map<K,V> See
map_filter()
.
-
transform_keys
(map<K1, V>, function) → MAP<K2,V> See
transform_keys()
.
-
transform_values
(map<K, V1>, function) → MAP<K,V2> See
transform_values()
.
-
map_keys
(x<K, V>) → array<K> Returns all the keys in the map
x
.
-
map_values
(x<K, V>) → array<V> Returns all the values in the map
x
.