igQueryでUTC(米国標準時）からJST(日本標準時）へ変更します

データの作成

WITH purchase_log AS (
  SELECT 'A' AS user_id, '2016-01-30' as last_date, '2016-01-30' as p_date, 'メロン' AS item UNION ALL
  SELECT 'A', 2017-12-30, 2016-01-30, '白菜' UNION ALL
  SELECT 'B', 2016-10-31, 2016-01-30, 'りんご' UNION ALL
  SELECT 'B', 2017-06-30, 2016-01-30, 'りんご' 
)
SELECT  * FROM purchase_log;

user_id	last_date	p_date	item
A	2016-01-30	2017-12-30	メロン
A	2017-12-30	2017-12-31	白菜
B	2016-10-31	2017-08-31	りんご
B	2017-06-30	2018-01-31	りんご

表示をJST(日本標準時）へ変更

SELECT
  user_id,
  last_date,
  -- 表示をJST(日本標準時）へ変更
  FORMAT_TIMESTAMP('%Y-%m-%d %H:%M:%S', last_date, 'Asia/Tokyo') AS JST
FROM 
  (
  SELECT
    user_id,
    CAST(last_date AS TIMESTAMP) AS last_date,
    CAST(p_date AS TIMESTAMP) AS p_date
  FROM
    test1.purchase_log
  );

| user_id | last_date | JST | | - | - | - | - | | A | 2016-01-30 00:00:00 UTC | 2016-01-30 09:00:00 | | A | 2017-12-30 00:00:00 UTC | 2017-12-30 09:00:00 | | B | 2016-10-31 00:00:00 UTC | 2016-10-31 09:00:00 | | B | 2017-06-30 00:00:00 UTC | 2017-06-30 09:00:00 |

参考サイト

【SQL】BigQueryで日付型を扱う