Hi Alexey, Consider this example: create table t20 (a varchar(10), b int); insert into t20 values ('red', 1), ('blue', 2), ('red',1001), ('blue', 1002); select json_objectagg(a,b) from t20; +----------------------------------------------+ | json_objectagg(a,b) | +----------------------------------------------+ | {"red":1, "blue":2, "red":1001, "blue":1002} | +----------------------------------------------+ the created object has multiple members with the same name. Is this expected or should be reported as a bug? In MySQL-8, the above example produces this: +-----------------------------+ | json_objectagg(a,b) | +-----------------------------+ | {"red": 1001, "blue": 1002} | +-----------------------------+ BR Sergei -- Sergei Petrunia, Software Developer MariaDB Corporation | Skype: sergefp | Blog: http://s.petrunia.net/blog