MariaDB [test]> SELECT JSON_CONTAINS('{"foo":"bar"}','{"foo":"bar"}');

+------------------------------------------------+

| JSON_CONTAINS('{"foo":"bar"}','{"foo":"bar"}') |

+------------------------------------------------+

|                                              0 |

+------------------------------------------------+

1 row in set (0.00 sec)

MariaDB [test]> SELECT JSON_CONTAINS('{"c": {"d": 4}}','{"d": 4}','$.c');

+---------------------------------------------------+

| JSON_CONTAINS('{"c": {"d": 4}}','{"d": 4}','$.c') |

+---------------------------------------------------+

|                                                 0 |

+---------------------------------------------------+

1 row in set (0.00 sec)

MySQL [test]> SELECT JSON_CONTAINS('{"foo":"bar"}','{"foo":"bar"}');

+------------------------------------------------+

| JSON_CONTAINS('{"foo":"bar"}','{"foo":"bar"}') |

+------------------------------------------------+

|                                              1 |

+------------------------------------------------+

1 row in set (0.00 sec)

MySQL [test]> SELECT JSON_CONTAINS('{"c": {"d": 4}}','{"d": 4}','$.c');

+---------------------------------------------------+

| JSON_CONTAINS('{"c": {"d": 4}}','{"d": 4}','$.c') |

+---------------------------------------------------+

|                                                 1 |

+---------------------------------------------------+

1 row in set (0.01 sec)