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map_concat

Description​

Returns the union of the input maps. If a key is found in multiple maps, this function keeps only the last value among these maps, called LAST WIN. For example, SELECT map_concat(map{1:3},map{1:'4'}); returns {1:"4"}.

This function is supported from v3.1 onwards.

Syntax​

ANY_MAP map_concat(any_map0, any_map1...)

Parameters​

any_mapN: the map values you want to union. All maps must share a common type. If data types of the input maps are not the same, the return type is the common supertype of the input maps.

Return value​

Returns a MAP of the common supertype of the input maps.

Examples​

mysql> SELECT map_concat(map('a',1, 'b',2), map('c',3));
+------------------------------------------+
| map_concat(map{'a':1,'b':2}, map{'c':3}) |
+------------------------------------------+
| {"c":3,"a":1,"b":2}                      |
+------------------------------------------+

mysql> select map_concat(map{1:3},map{'3.323':3});
+--------------------------------------+
| map_concat(map{1:3}, map{'3.323':3}) |
+--------------------------------------+
| {"3.323":3,"1":3}                    |
+--------------------------------------+


mysql> select map_concat(map{1:3},map{1:'4', 3:'5',null:null}, null);
+--------------------------------------------------------+
| map_concat(map{1:3}, map{1:'4',3:'5',NULL:NULL}, NULL) |
+--------------------------------------------------------+
| {null:null,1:"4",3:"5"}                                |
+--------------------------------------------------------+