MySQL 8.0

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SELECT VERSION();


VERSION()


8.0.36


SELECT
  CAST( 
    CONCAT('["', REPLACE('a,b,c,d', ',', '","'), '"]')
    AS JSON
  ) INTO @`json_array`;
SELECT
  @`json_array`,
  JSON_TYPE(@`json_array`);


@`json_array`
JSON_TYPE(@`json_array`)


["a", "b", "c", "d"]
ARRAY