create-table-alter-enum-column-to-array-of-that-enum

-- CreateEnum
CREATE TYPE "Hobby" AS ENUM ('ENTREPRENEUR', 'SPORT', 'MUSIC', 'MOVIE', 'CODING', 'TRAVELING', 'WORKING', 'LEARNING');

-- CreateTable
CREATE TABLE "tasks" (
    "id" SERIAL NOT NULL,
    "firstname" VARCHAR(100) NOT NULL,
    "imageId" VARCHAR(36) NOT NULL,
    "hobbies" "Hobby" NOT NULL DEFAULT E'LEARNING',
    "favoriteNumbers" INTEGER[],

    CONSTRAINT "tasks_pkey" PRIMARY KEY ("id")
);

-- But this migration fails because I have records that their hobbies is full
-- AlterTable
ALTER TABLE "tasks" ALTER COLUMN "hobbies" DROP DEFAULT,
ALTER COLUMN "hobbies" SET DATA TYPE "Hobby"[];

-- You have to use USING:
ALTER TABLE "tasks" ALTER COLUMN "hobbies" DROP DEFAULT,
ALTER COLUMN "hobbies" SET DATA TYPE "Hobby"[] USING ARRAY["hobbies"];