Hi,
如果兩次 left join 的話是否滿足你的需求呢？
然後在取 temporal table 的字段時，用 IF 去判斷取值。參考 SQL 如下
SELECT
c.mer_cust_id,
*IF(k.mer_cust_id IS NOT NULL AND a.mercust_id IS NOT NULL AND
k.mer_cust_id <> '', k.update_time, NULL) AS update_time*
FROM charge_log as c
LEFT JOIN ka_mer_info FOR SYSTEM_TIME AS OF c.proc_time AS k
ON c.mer_cust_id = k.mer_cust_id
LEFT JOIN adp_mer_user_info FOR SYSTEM_TIME AS OF c.proc_time AS a
ON c.mer_cust_id = a.mer_cust_id
不過，這種寫法只能適用在兩張 MySQL 表都保證 mer_cust_id 是唯一主鍵的狀況下。如果 mer_cust_id
不是唯一的話，輸出的結果數量會跟原本提供的 SQL 期望的輸出不一致
比如說 ka_mer_info 有 0 筆數據， adp_mer_user_info 有 2 筆數據，原先的 SQL 會得到 1 筆 left
join 沒成功的數據，上面提供的 SQL 則會輸出 2 筆。
casel.chen <casel_c...@126.com> 於 2021年12月1日 週三 下午6:33寫道：
> lookup join用的维表需要从两张mysql表做关联后得到，因此创建了一个视图。但发现flink sql不支持lookup
> join关联视图，会抛
> Temporal Table Join requires primary key in versioned table, but no
> primary key can be found.
>
>
> 请问这种情况要怎么解决？
>
>
> CREATE VIEW query_mer_view (mer_cust_id, update_time) AS
> SELECT a.mer_cust_id, k.update_time
> FROM ka_mer_info k INNER JOIN adp_mer_user_info a on k.mer_cust_id =
> a.mer_cust_id
> where k.mer_cust_id <> '';
>
>
> SELECT
> DATE_FORMAT(c.create_time, 'yyyy-MM-dd') AS payment_date,
> c.mer_cust_id,
>
>
> c.trans_amt,
> CASE c.trans_stat WHEN 'S' THEN c.trans_amt ELSE 0 END as
> succ_amt ,
>
>
> 1 as trans_cnt,
> CASE c.trans_stat WHEN 'S' THEN 1 ELSE 0 END as succ_cnt ,
> CASE c.trans_stat WHEN 'F' THEN 1 ELSE 0 END as fail_cnt
>
>
> FROM charge_log as c
> LEFT JOIN query_mer_view FOR SYSTEM_TIME AS OF
> c.proc_time AS q
> ON c.mer_cust_id = q.mer_cust_id;
