SQL(bq)での出力について

SQL(bq)の処理について質問です。
以下のクエリであるjancodeの購入回数を期間ごとに取得しています。
今回の例でいうと'2020/11'の場合の値がテーブルに無いので出力されないのですが
こちらを0として出力したいです

想定イメージ
period purchase_user trial_user repeat_user
2020/05 6 6 0
2020/08 6 6 0
2020/11 0 0 0

CREATE TABLE
  [project_id].}[dataset_name].[table_name]
(
  user_id STRING
  , start_date DATE
  , end_date DATE
  , date DATE
  , jancode STRING
)
;

INSERT INTO [project_id].}[dataset_name].[table_name]
VALUES('00','2022-05-01','2022-05-31','2020-05-02','12345678')
    , ('01','2022-05-01','2022-05-31','2020-05-12','12345678')
    , ('02','2022-05-01','2022-05-31','2020-05-13','12345678')
    , ('03','2022-05-01','2022-05-31','2020-08-02','12345678')
    , ('04','2022-05-01','2022-05-31','2020-08-02','12345678')
    , ('05','2022-05-01','2022-05-31','2020-08-01','12345678')
    , ('06','2022-05-01','2022-05-31','2020-09-04','12345678')
    , ('07','2022-05-01','2022-05-31','2020-05-02','12345678')
    , ('08','2022-05-01','2022-05-31','2020-09-02','12345678')
    , ('09','2022-05-01','2022-05-31','2020-05-02','12345678')
    , ('10','2022-05-01','2022-05-31','2020-09-02','12345678')
    , ('11','2022-05-01','2022-05-31','2020-05-02','12345678')
;

WITH test AS (
SELECT
 CASE WHEN date BETWEEN DATE_SUB(start_date, INTERVAL 24 MONTH) AND DATE_SUB(end_date, INTERVAL 22 MONTH) THEN '2020/05'
      WHEN date BETWEEN DATE_SUB(start_date, INTERVAL 21 MONTH) AND DATE_SUB(end_date, INTERVAL 19 MONTH) THEN '2020/08'
      WHEN date BETWEEN DATE_SUB(start_date, INTERVAL 18 MONTH) AND DATE_SUB(end_date, INTERVAL 16 MONTH) THEN '2020/11'
      END AS period
 , user_id
 , COUNT(DISTINCT date) AS frequency
FROM
  [project_id].}[dataset_name].[table_name]
WHERE
 jancode = '12345678' 
GROUP BY
 user_id
 , period
)
 SELECT
 period
 , COUNT(DISTINCT user_id) AS purchase_user
 , COUNT(DISTINCT IF(frequency = 1, user_id,NULL)) AS traial_user
 , COUNT(DISTINCT IF(frequency > 1, user_id,NULL)) AS repeat_user
FROM
 test
GROUP BY
 period
ORDER BY
 period