text: ALTER TABLE "users"
  DROP COLUMN "mine";
  
  --------------------------------------------------------------------------------
  
  CREATE TYPE MINING_TYPE AS ENUM (
    'mine',
    'withdraw'
  );
  
  CREATE TABLE "mining" (
    "mining_id" SERIAL      NOT NULL,
    "user_id"   INTEGER     NOT NULL REFERENCES "users"("user_id"),
    "type"      MINING_TYPE NOT NULL,
    "amount"    FLOAT       NOT NULL,
    "time"      TIMESTAMP   WITHOUT TIME ZONE DEFAULT NOW(),
  
    PRIMARY KEY("mining_id")
  );
  