DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a JSON);

INSERT INTO t1 VALUES ('{"a":"b"}');

SELECT a, JSON_COMPACT(a), COALESCE(a) FROM t1;

MariaDB [test]> SELECT a, JSON_COMPACT(a), COALESCE(a) FROM t1;

Field   1:  `a`

Org_field:  `a`

Catalog:    `def`

Database:   `test`

Table:      `t1`

Org_table:  `t1`

Type:       BLOB (format=json)

Collation:  utf8_general_ci (33)

Length:     4294967295

Max_length: 9

Decimals:   0

Flags:      BLOB BINARY 

Field   2:  `JSON_COMPACT(a)`

Org_field:  ``

Catalog:    `def`

Database:   ``

Table:      ``

Org_table:  ``

Type:       LONG_BLOB (format=json)

Collation:  utf8_general_ci (33)

Length:     4294967295

Max_length: 9

Decimals:   0

Flags:      BINARY 

Field   3:  `COALESCE(a)`

Org_field:  ``

Catalog:    `def`

Database:   ``

Table:      ``

Org_table:  ``

Type:       LONG_BLOB

Collation:  utf8_general_ci (33)

Length:     4294967295

Max_length: 9

Decimals:   39

Flags:      BINARY 

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

| a         | JSON_COMPACT(a) | COALESCE(a) |

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

| {"a":"b"} | {"a":"b"}       | {"a":"b"}   |

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

1 row in set (0.000 sec)